(Not sure if this is the proper place to post, but I'm sure I don't know a better place to ask)

My partner and myself got new (EU) passports last year, issued in Belgium (Belgian nationality, no other nationalities or anything that could flag us). We used them for travel BRU > IAD, DCA > BOS, BOS > FRA and FRA > BRU.

• BRU and FRA: no problems. e-Gates worked without any glitch for both of us.
• IAD: only arrived there, passport was checked by CBP in-person, nothing mentioned
• DCA and BOS (at TSA check-point): computer system would not accept either of our passports. Supervisor needed to be called, and after lengthy wait and a glance at our passport, the system was overridden and we were told to move on.
  • None of the airlines (UA, JBU, LH) had any issues with our passports

At BOS I dared to go back and ask if something was wrong with our passports. The few words we got out of the agent was "it's something with the UV"...

I'm posting here to see if anyone had similar experience, or advice on what could be happening here?
I'm most concerned that - on a future occasion - this could lead to excessive delays that would ultimately result in a missed flight. Since the EU gates seem to be perfectly happy with our passports, I'm expecting to get turned away by our city hall if I would claim the passports are defective.