Hello  Futureguard

I have not seen these changes recently.   Possibly an update may reset stuff.  Version 2022  in PU 1 and PU2 changes   for Customizer which addressed errors related to custom panels being updated. are listed in the release notes.  
I've always found troubleshooting custom panels confusing.  Too many variables.  Simplest way for me is going to where the issue is visible.  Then right click in a blank area and select System Information  Depending on the custom panel and where the entry originated , the panel selection might be the issue. 

example customizing the AR Invoice history inquiry panel.  There is the ARLines and the SOLines selection.  In most instances the default would be ARLines, unless  you were viewing record that was  Source SO, then it would pull up the SOLines.  I would check if you can see your changes  in either.    
    

Hope this helps

Hello  Futureguard

I have not seen these changes recently.   Possibly an update may reset stuff.  Version 2022  in PU 1 and PU2 changes   for Customizer which addressed errors related to custom panels being updated. are listed in the release notes.  
I've always found troubleshooting custom panels confusing.  Too many variables.  Simplest way for me is going to where the issue is visible.  Then right click in a blank area and select System Information  Depending on the custom panel and where the entry originated , the panel selection might be the issue. 

example customizing the AR Invoice history inquiry panel.  There is the ARLines and the SOLines selection.  In most instances the default would be ARLines, unless  you were viewing record that was  Source SO, then it would pull up the SOLines.  I would check if you can see your changes  in either.    
    

Hope this helps