Error on template file using button visual - unable to access the format pane

Thanks for the reply, apologies, I had originally stated that I thought this may be due to corruption but then removed it as I thought I could not recreate the same error as the starter file I used opened without the error.  But in following the full process to create the pbit then open it as a new untitle pbix file, the error does occur consistently.  Skip to the last 2 paragraphs for what I discovered was the difference...

Other things I tried to troubleshoot:

I have cleared the cache and the same happens.  I reinstalled Power BI yesterday, and this is occurring for multiple users, so don't think it's going to change if i did it again today.

I recreated the URL measure exactly as it was in the original, including the same table name and display folder name - but no change - the error is there if the measure exists or not.

I've grouped the button and ungrouped it again.  I've hidden the visual and unhidden it.  No change in any of these states.  (I read this as a solution on another post where the format pane was not visible for a visual.)

I have tried to save the starter file as a pbip, to access the TMDL files to look for issues, but couldn't see anything in the TMDL or JSON files (could be my inexperience with TMDL).

I have recreated the pbit file from the starter file with a brand new button visual and the same error occurs once I open the template.

I have created a brand new file with 3 example buttons, one assigned to back action, one to a Web URL that I typed in, and one assigned a Web URL by a measure conditionally.  In saving this new file as a pbit and then opening it, it was fine.  I suspected the difference might have been the application of a theme file, so applied the same theme file and saved as a pbit, upon opening it was again fine.  Eventually I discovered the difference was in deleting all data tables including the measure from the starter file just before I create the pbit (which I have been doing purposefully for months as we are using import and direct lake modes, so we don't want a local model created).  As soon as the measure is delete the error appears on the visual and even if the measure is added straight back in under the same structure and naming format the visual is broken and cannot have it's format properties accessed/edited.  The only thing that can be done is to delete the visual and recreate - against the priciple of having a template.  Sigh.

So I am now assuming there has been a change applied, as this was working upon realease and for months beforehand.  If I leave a URL measure in place, the resulting file created from using the template is mixed mode, so need to be sure if this will mean all my direct lake table connects will fallback to direct query as I presume they will (not an option for us).