[4.4.0.58] Losing cellular (not data) connection when crossing country borders

REPRODUCIBILITY: Always (but I only did it twice)
OS VERSION: 4.4.0.58
HARDWARE: Xperia X Compact (and Xperia 10 II although I am not sure, if anyone was trying to call me. Iirc the roaming SMS only arrived after a restart)
UI LANGUAGE: German
REGRESSION: Yes

DESCRIPTION:

When driving by car or by train from Germany to Austria, the phone switches to roaming mode (the triangle). From that point on I seem to not be able to receive calls or SMS anymore, but I can still use the internet as before. They are just silently dropped or arrive only after a restart.

PRECONDITIONS:

Live close enough to a country border. Only tried Germany-Austria so far.

STEPS TO REPRODUCE:

  1. Check if people can call you
  2. Cross border
  3. Check if people can still call you

EXPECTED RESULT:

People can call me even after switching countries.

ACTUAL RESULT:

No calls arrive

MODIFICATIONS:

ADDITIONAL INFORMATION:

Don’t have any, since I was in a bit of a rush ._.