To reproduce : find a field with a t subfield (700) edit a marc framework with this subfield click on Advanced constraints
To clarify : this only happens in the 't' tab, there is no problem with the other subfields.
This problem only happens if you have adblock plus installed and activated in firefox it seems.
There is a rule in adblock plus : ###advt that blocks the display of the advanced constraint tab with the advt id.
This problem is due to another extension and should be fixed there. A separate bug has been submitted to the adblock plus team. Meanwhile, if you encounter the bug, check your adblock plus rules or deactivate the extension.
I've send a report : https://reports.adblockplus.org/a506530c-65f9-426b-9246-75c181db10e4#tab=requests