Problem using a droplist based on an option set to provide a repeating group constraint

I’m trying and failing to do something which I hoped would be pretty simple. I guess it is but I’m missing something. I have a table of data based on a reconciliationtask data type which I am providing droplist filters for. One of the droplists maps to a Transaction Type Option Set.

The droplist works on the page OK, but I cannot bind it to the constraint underlying the repeating group on the page. The other two droplists, based on text data, are fine.

Here is the droplist configuration:

…and here is what happens when I try to add to the constraint for the repeating group:

As you can see “Dropdown Type” is not available and has the message “incompatible type”. It feels to me that the types match, as the droplist is collecting “Transaction Types” and the filter is on the field made up of “Transaction Types”. What am I missing?

Thanks in advance for any help you can offer. I can change the underlying data types if necessary, but I assume there’s a way to solve it this way.

What is the “type” of "type field? Is it a text? Or option set Transaction types?

It’s Transaction Type (option set).

First: report this to Bubble support. It’s probably a bug (I’Ve seen this often in the past and this have been reported here too)

Try to refresh page (sometimes it’s enough to fix that)
Now workaround:
Use the only when section or conditionnal that is empty to set Dropdown Type’s value, right click to copy expression (even if this is red), and paste it in type of your search. Clear the only when or conditionnal you used to put the expression.

it’s a bug. it’s been happening for a few weeks now. either copy the expression from another place or use :filtered