Weird "mautic.core..." elements in menus

Your software
My Mautic version is: 4.0.1
My PHP version is: 7.4.23
My Database type and version is: 5.7.35-cll-lve

Your problem
My problem is:
Instead of seeing regular expressions on buttons I see some unusual expressions, that all start with “mautic.core.” Please see the screenshot.
I used earlier version of Mautic (3.3) and it happened then. After that I updated Mautic
and it was fine for a short period of time and now it’s back again.

These errors are showing in the log:
[2021-10-04 04:28:33] mautic.WARNING: PHP Warning - Illegal string offset ‘regex’ - in file /home/agnms/ma.agencija-ms.com/vendor/matomo/device-detector/Parser/AbstractParser.php - at line 344 {“val1”:null,“val2”:"/home/agnms/ma.agencija-ms.com/vendor/matomo/device-detector/regexes/bots.yml"}
[2021-10-04 04:28:33] mautic.WARNING: PHP Warning - Illegal string offset ‘regex’ - in file /home/agnms/ma.agencija-ms.com/vendor/matomo/device-detector/Parser/Client/Browser.php - at line 486 {“regex”:"/home/agnms/ma.agencija-ms.com/vendor/matomo/device-detector/regexes/client/browsers.yml"}
[2021-10-04 06:03:30] mautic.WARNING: PHP Warning - Illegal string offset ‘regex’ - in file /home/agnms/ma.agencija-ms.com/vendor/matomo/device-detector/Parser/AbstractParser.php - at line 344 {“val1”:null,“val2”:"/home/agnms/ma.agencija-ms.com/vendor/matomo/device-detector/regexes/bots.yml"}
[2021-10-04 06:03:30] mautic.WARNING: PHP Warning - Illegal string offset ‘regex’ - in file /home/agnms/ma.agencija-ms.com/vendor/matomo/device-detector/Parser/Client/Browser.php - at line 486 {“regex”:"/home/agnms/ma.agencija-ms.com/vendor/matomo/device-detector/regexes/client/browsers.yml"}
[2021-10-04 06:03:41] mautic.WARNING: PHP Warning - Illegal string offset ‘regex’ - in file /home/agnms/ma.agencija-ms.com/vendor/matomo/device-detector/Parser/AbstractParser.php - at line 344 {“val1”:null,“val2”:"/home/agnms/ma.agencija-ms.com/vendor/matomo/device-detector/regexes/bots.yml"}
[2021-10-04 06:03:41] mautic.WARNING: PHP Warning - Illegal string offset ‘regex’ - in file /home/agnms/ma.agencija-ms.com/vendor/matomo/device-detector/Parser/Client/Browser.php - at line 486 {“regex”:"/home/agnms/ma.agencija-ms.com/vendor/matomo/device-detector/regexes/client/browsers.yml"}
[2021-10-04 06:03:48] mautic.WARNING: PHP Warning - Illegal string offset ‘regex’ - in file /home/agnms/ma.agencija-ms.com/vendor/matomo/device-detector/Parser/AbstractParser.php - at line 344 {“val1”:null,“val2”:"/home/agnms/ma.agencija-ms.com/vendor/matomo/device-detector/regexes/bots.yml"}
[2021-10-04 06:03:48] mautic.WARNING: PHP Warning - Illegal string offset ‘regex’ - in file /home/agnms/ma.agencija-ms.com/vendor/matomo/device-detector/Parser/Client/Browser.php - at line 486 {“regex”:"/home/agnms/ma.agencija-ms.com/vendor/matomo/device-detector/regexes/client/browsers.yml"}
[2021-10-04 06:11:59] mautic.WARNING: PHP Warning - Illegal string offset ‘regex’ - in file /home/agnms/ma.agencija-ms.com/vendor/matomo/device-detector/Parser/AbstractParser.php - at line 344 {“val1”:null,“val2”:"/home/agnms/ma.agencija-ms.com/vendor/matomo/device-detector/regexes/bots.yml"}
[2021-10-04 06:11:59] mautic.WARNING: PHP Warning - Illegal string offset ‘regex’ - in file /home/agnms/ma.agencija-ms.com/vendor/matomo/device-detector/Parser/Client/Browser.php - at line 486 {“regex”:"/home/agnms/ma.agencija-ms.com/vendor/matomo/device-detector/regexes/client/browsers.yml"}
[2021-10-04 06:13:09] mautic.WARNING: PHP Warning - Illegal string offset ‘regex’ - in file /home/agnms/ma.agencija-ms.com/vendor/matomo/device-detector/Parser/AbstractParser.php - at line 344 {“val1”:null,“val2”:"/home/agnms/ma.agencija-ms.com/vendor/matomo/device-detector/regexes/bots.yml"}
[2021-10-04 06:13:09] mautic.WARNING: PHP Warning - Illegal string offset ‘regex’ - in file /home/agnms/ma.agencija-ms.com/vendor/matomo/device-detector/Parser/Client/Browser.php - at line 486 {“regex”:"/home/agnms/ma.agencija-ms.com/vendor/matomo/device-detector/regexes/client/browsers.yml"}
[2021-10-04 06:17:18] mautic.WARNING: PHP Warning - Illegal string offset ‘regex’ - in file /home/agnms/ma.agencija-ms.com/vendor/matomo/device-detector/Parser/AbstractParser.php - at line 344 {“val1”:null,“val2”:"/home/agnms/ma.agencija-ms.com/vendor/matomo/device-detector/regexes/bots.yml"}
[2021-10-04 06:17:18] mautic.WARNING: PHP Warning - Illegal string offset ‘regex’ - in file /home/agnms/ma.agencija-ms.com/vendor/matomo/device-detector/Parser/Bot.php - at line 75 {“result”:null,“regex”:"/home/agnms/ma.agencija-ms.com/vendor/matomo/device-detector/regexes/bots.yml"}
[2021-10-04 06:17:18] mautic.CRITICAL: Uncaught PHP Exception Symfony\Component\Debug\Exception\FatalThrowableError: “Cannot unset string offsets” at /home/agnms/ma.agencija-ms.com/vendor/matomo/device-detector/Parser/Bot.php line 78 {“exception”:"[object] (Symfony\Component\Debug\Exception\FatalThrowableError(code: 0): Cannot unset string offsets at /home/agnms/ma.agencija-ms.com/vendor/matomo/device-detector/Parser/Bot.php:78)"}
[2021-10-04 06:24:51] mautic.WARNING: PHP Warning - Illegal string offset ‘regex’ - in file /home/agnms/ma.agencija-ms.com/vendor/matomo/device-detector/Parser/AbstractParser.php - at line 344 {“val1”:null,“val2”:"/home/agnms/ma.agencija-ms.com/vendor/matomo/device-detector/regexes/bots.yml"}
[2021-10-04 06:24:51] mautic.WARNING: PHP Warning - Illegal string offset ‘regex’ - in file /home/agnms/ma.agencija-ms.com/vendor/matomo/device-detector/Parser/Client/Browser.php - at line 486 {“regex”:"/home/agnms/ma.agencija-ms.com/vendor/matomo/device-detector/regexes/client/browsers.yml"}

Steps I have tried to fix the problem:
Cleared cache