Block in localized fields crashing Pimcore Admin

i am using Pimcore 6.8.4 set up locally on docker using skeleton from 2.8.7 release and i found strange issue.

I created a simple data object with localizedfields and block put in it, when i fill it with data , whole folder in pimcore admin, where this data object is located, stops listing properly. There is an error in browser console:

    Error: You're trying to decode an invalid JSON String: {"offset":0,"limit":30,"total":"1","overflow":false,"nodes":[{"id":3,"idx":0,"key":"test","sortBy":"key","sortOrder":"ASC","text":"test","type":"object","path":"\/test\/test","basePath":"\/test\/","elementType":"object","locked":false,"lockOwner":false,"isTarget":true,"allowDrop":true,"allowChildren":true,"leaf":false,"cls":"pimcore_class_icon  ","published":true,"className":"test","allowVariants":null,"icon":null,"iconCls":"pimcore_icon_object","qtipCfg":{"title":"ID: 3","text":"Type: test"},"expanded":true,"permissions":{"save":true,"unpublish":true,"lEdit":true,"lView":true,"layouts":true,"list":true,"view":true,"publish":true,"delete":true,"rename":true,"create":true,"settings":true,"versions":true,"properties":true},"expandable":false,"loaded":true}],"fromPaging":0,"filter":"","inSearch":0}<br />
<b>Fatal error</b>:  Uncaught Error: Call to undefined method Pimcore\Model\Element\ElementDescriptor::getClass() in /var/www/html/vendor/pimcore/pimcore/models/DataObject/Localizedfield.php:374
Stack trace:
#0 /var/www/html/vendor/pimcore/pimcore/models/DataObject/Localizedfield.php(757): Pimcore\Model\DataObject\Localizedfield-&gt;getFieldDefinitions(Array, Array)
#1 /var/www/html/vendor/pimcore/pimcore/models/DataObject/Localizedfield.php(632): Pimcore\Model\DataObject\Localizedfield-&gt;getLazyLoadedFieldNames()
#2 [internal function]: Pimcore\Model\DataObject\Localizedfield-&gt;__sleep()
#3 /var/www/html/vendor/pimcore/pimcore/lib/Cache/Core/CoreHandler.php(610): serialize(Object(Pimcore\Model\DataObject\Test))
#4 /var/www/html/vendor/pimcore/pimcore/lib/Cache/Core/CoreHandler.php(905): Pimcore\Cache\Core\CoreHandler-&gt;storeCacheItem(Object(Pimcore\Cache\Pool\CacheItem), Object(Pimcore\Model\DataObject\Test), false)
#5 /var/www/html/vendor/pimcore/pimcore/lib/Cache/Core/CoreHandler.php(954): Pimcore\Cache\Core\CoreHandler-&gt;writeSaveQu in <b>/var/www/html/vendor/pimcore/pimcore/models/DataObject/Localizedfield.php</b> on line <b>374</b><br />

    at new Ext.Error (ext-all.js?_dc=e2d8837a46ce0a99711be8cc5927418bb221286b:22)
    at Function.raise (ext-all.js?_dc=e2d8837a46ce0a99711be8cc5927418bb221286b:22)
    at Object.Ext.raise (ext-all.js?_dc=e2d8837a46ce0a99711be8cc5927418bb221286b:22)
    at Object.Ext.JSON.me.decode (ext-all.js?_dc=e2d8837a46ce0a99711be8cc5927418bb221286b:22)
    at g.onProxyLoad (script-proxy?scripts=minified_javascript_core_f3dddc68b1910f2e6f1d1cdfc8fb43ad.js&_dc=e2d8837a46ce0a99711be8cc5927418bb221286b:7387)
    at E.triggerCallbacks (ext-all.js?_dc=e2d8837a46ce0a99711be8cc5927418bb221286b:22)
    at E.setCompleted (ext-all.js?_dc=e2d8837a46ce0a99711be8cc5927418bb221286b:22)
    at E.setException (ext-all.js?_dc=e2d8837a46ce0a99711be8cc5927418bb221286b:22)
    at E.process (ext-all.js?_dc=e2d8837a46ce0a99711be8cc5927418bb221286b:22)
    at E.processResponse (ext-all.js?_dc=e2d8837a46ce0a99711be8cc5927418bb221286b:22)

No matter if it is clean skeleton that has nothing in it, or my project that im working at, it’s not working.
I tried to replicate it in my other projects on earlier pimcore versions and it works like charm, also tried to do that on public pimcore demo - it works fine. But not on skeleton release. Why? And is there a way to fix that?