Graffx Design OK cool if the cache problem is not there anymore.
I'm in the process of migrating, I will tell you if I see something bad.
For your YAMs error with PHP 8.2. I'm still in PHP 7.4 so I can't try it but I confirm, it's a PHP 8 restriction.
What is your YAMs version, 1.3.1 ? I haven't the same line 288 in yams.plugin.inc.php !
(check the version in assets/modules/yams/README.md)
EDIT : OK, It seems that you are still in v 1.2.0-RC3 or RC6, but I developed in 2020 a new v1.3.0 based on the Deesen v1.2.0-RC7. This line if( ! array_key_exists( $tvIdentifier, $tmplvars ) ) is not in the RC7 code anymore ...
v1.3.0 is for Evo 2.x and php 7.4 compatibility, I've been running this for 5 years in Evo 2.x without any problem. I'll check if I get this bug in v3.1.10. I'm not sure if YAMs v1.3.1 is ok with php 8 so don't upgrade until I'll tell you.
This is my plan :
-1. upgrade to evo 3.1.10 (last evo version that accept php7.4)
1.1. check and adapt Yams for evo V3 and php 8 compatibility => maybe new Yams release
-2. migrate my server to php8
-3. migrate to evo 3.2
3.1 consider a migration plan (if possible) to sLang (because sLang needs Evo 3.2 so I can't do it in 1.)
I'll share it for all people that refrain migrating to V3 because of Yams. Having in mind that the goal is to switch to sLang when possible.