MrRoboto1212 A few hours after this post, i switched to APKMirror version of Messages, successfully updated via Play Store, and RCS worked for a day again before flashing the 3000 / 3200 error.
Anyone under T-Mobile who's able to permanently fix this issue, please reply to me. Many users would greatly appreciate it. Not sure if the pool of users who this affects is large enough to warrant study time and a solid fix from the GOS team...