Example URL & Send Example don't find contacts

Your software
My Mautic version is: 5.2.4
My PHP version is: 8.2
My Database type and version is: MySQL 5.7

Your problem
My problem is:
When trying to either generate a user specific preview URL or send an example email, the contact search never returns a contact. I’m not sure if I’m not using them right, which fields can be used for these or if it’s because we have around 6M contacts?

Even with sending an example to a manually entered email, that dialog doesn’t seem to respond - Send and Cancel don’t close the dialog or send an email.

These errors are showing in the log:
Chrome console shows this when opening the dialog:
app.js?v611ae260:96 Uncaught TypeError: Mautic[callback] is not a function
at HTMLInputElement. (app.js?v611ae260:96:252)
at jQuery.each (libraries.js?v611ae260:98:212)
at jQuery.fn.init.each (libraries.js?v611ae260:89:190)
at Mautic.activateLookupTypeahead (app.js?v611ae260:96:104)
at Mautic.onPageLoad (app.js?v611ae260:71:352)
at Mautic.processModalContent (app.js?v611ae260:358:8)
at Object.success (app.js?v611ae260:349:130)
at fire (libraries.js?v611ae260:274:351)
at Object.fireWith [as resolveWith] (libraries.js?v611ae260:279:179)
at done (libraries.js?v611ae260:670:95)

Then if cancel is clicked, shows slightly different error:
11app.js?v611ae260:96 Uncaught TypeError: Mautic[callback] is not a function
at HTMLInputElement. (app.js?v611ae260:96:252)
at jQuery.each (libraries.js?v611ae260:98:212)
at jQuery.fn.init.each (libraries.js?v611ae260:89:190)
at Mautic.activateLookupTypeahead (app.js?v611ae260:96:104)
at Mautic.onPageLoad (app.js?v611ae260:71:352)
at Mautic.processModalContent (app.js?v611ae260:358:8)
at app.js?v611ae260:287:194
at Object.success (app.js?v611ae260:293:33)
at options.success (libraries.js?v611ae260:1629:134)
at fire (libraries.js?v611ae260:274:351)