Problem with placeholders in Eval populate

[johnonorvic]

I am designing a form which is working so far. Before adding some new features, I updated Joomla and Fabrik, from 3.9.16/3.9 to 3.9.20/3.9.2. Having done so (and changed nothing else) parts of the form ceased to work properly. I found that placeholders in the Eval populate of a drop down element of the form were returning blank data (a 0 value or an empty string). Having made a backup before the update, I was able to restore the backup to a new sub-domain. This worked as before with the placeholders returning the correct data.

An online search revealed no relevant information and, while I cannot believe a basic Fabrik feature could stop working without anyone noticing, I cannot think what else is making the difference.

The only code (just for monitoring; everything else now removed) in the Eval populate in each system is:

dump((int)'{v_membership_details___AbilityGroup}', 'v_membership_details___AbilityGroup');
dump('{v_membership_details___MembershipClass}', 'v_membership_details___MembershipClass');​

I use J!Dump for monitoring. In the updated system it shows:

[integer] v_membership_details___AbilityGroup = 0
[string] v_membership_details___MembershipClass = ""​

and in the original system it shows (correctly):

[integer] v_membership_details___AbilityGroup = 1
[string] v_membership_details___MembershipClass = "1"​

Can anyone please suggest what might be going on?