When I try to remove relationship records using the many to many format, the screen goes blank with only the message:
'Are you sure you want to remove the following records from the relationship'
appearing at the top of the screen.
This happens in a database that I have and also in my LCMS site.
In looking at the code for RemoveRelatedRecordForm.php, I did notice that you use echo in the display() function. This is different from the way you have build the display() function in DeleteForm.php.
I did try to remove the translate function in the echo message to see if it would make a difference and it didn't.
André