# Error after upgrading to 4.2 clearing cache fails and error: Unknown column last\_built\_date in field list

**URL:** <https://forum.mautic.org/t/error-after-upgrading-to-4-2-clearing-cache-fails-and-error-unknown-column-last-built-date-in-field-list/22866>\
**Category:** Mautic 4 Install/Upgrade Support\
**Created:** [March 1, 2022, 4:08pm UTC](https://forum.mautic.org/t/error-after-upgrading-to-4-2-clearing-cache-fails-and-error-unknown-column-last-built-date-in-field-list/22866 "2022-03-01T16:08:50Z")\
**Posts on this page:** 1\
**Showing post:** 4

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**Author:** ![silavapi](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.mautic.org/silavapi/32/7424_2.png) [@silavapi](https://forum.mautic.org/u/silavapi)\
**Post date:** [March 1, 2022, 4:35pm UTC](https://forum.mautic.org/t/error-after-upgrading-to-4-2-clearing-cache-fails-and-error-unknown-column-last-built-date-in-field-list/22866/4 "2022-03-01T16:35:53Z")

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Right - @tobsowo had a similar problem. Other than the usual ‘don’t update in the browser’ message, here’s what helped him:

1. Clear the cache by deleting the cache folder
2. Follow these steps:

> **[Mautic update failed - how to recover](https://docs.mautic.org/en/troubleshooting/update-failed)**
>
> . Sometimes when updating Mautic, the process might stall or fail part way through. This can cause a problem, because it can cause Mautic to be inbetween two versions and often this can make the system unusable.. . . . . . Generally speaking, updates...

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_[View the full topic](https://forum.mautic.org/t/error-after-upgrading-to-4-2-clearing-cache-fails-and-error-unknown-column-last-built-date-in-field-list/22866)._