[joecool1029]

When signal is poor it's likely locking to the band 12 layer (700mhz) which is only 5mhz x 5mhz worth of bandwidth. It congests easier than band4 which is typically 20x20. For whatever reason iphones seem to be a bit stickier to this band, probably due to weaker antennas or firmware that kicks it off the beefier bands faster.

[thinkythought]

There's something to this theory, as switching airplane mode off and on usually results in a usable connection. This is still completely unacceptable behavior though, and i haven't been able to replicate it on multiple other devices i have handy(including other iphones, including ones with band 12 support)

[joecool1029]

My experience with the SE has been that it goes to band 12 first or if its moving fast within a cell. Then it ‘settles’ into band 4 or 2 on tmobile after about a minute.

My old modem phone I purposefully got without band 12 because it saturates so easy, now I just lock bands and speedtest until I find most reliable with the current.