How do you determine that?
The Q26 istelf does not report signal strength in “bars”…
I had a problem with one client using an international roaming SIM - in certain cases, it would fail to register even though AT+COPS=? showed that it could “see” permitted networks.
However, this was after losing coverage - I don’t know about “first registration”.
Apparently, this SIM had some sort of “least-cost algorithm” to determine which network to choose - so that might have had something to do with it.
Does issuing AT+COPS=0 help?
See: Undocumented side-effect of AT+COPS=0 - #2 by szalik