Hi, I'm living in Malaysia.
I'm also facing unstable connectivity issue on Band3/7 with my Pro1X.
My finding is when I traveled to Thai last week, connectivity was OK.
At that time, I didn't check which Band was connected, but it seems Band1 is common in Thai.
Besides, I'm checking Japanese BBS about Pro1/Pro1x recently.
No one report connectivity issue as far as I know.
Band1 is common in Japan as well.