-134 signal on ANT1 is basically not usable. you really want to get to greater than -110 for tmobile 5G to stick.
according to https://www.quectel.com/wp-content/uploads/2021/04/Quectel_RM500Q-AERM502Q-AE_Hardware_Design_V1.0.pdf
ANT0 supports 1400-5000Mhz and ANT1 and ANT2 supports 600-6000/5000Mhz. n71 is 600Mhz so that might be your issue since ANT1 signal is really low. You might want to adjust your antenna to get a better signal for ANT1 and enable the other ports to use ANT1&2 instead of ANT0&1 since 600Mhz is only on those and another user reported they are able to run 2x2 only ANT1 and ANT2
Also AT+QNWPREFCFG=“nr5g_disable_mode”,1 disables only SA, but you lose all 5G because you are not able to connect to NSA due to possibly signal issue. It’s better to leave all the setting to auto or default unless you need band locking.