“If Ms is attached on a VPLMN from another country, it’ss not try to return back home.”
1) Unless of course the mobile switches off and then on then it will check for HPLMN
2) or as this a border case with neighbour VPLMN what happens with handover. MS usually detect 7 (one cammped and 6 neighbours). If MS moving toward HPLMN from VPLMN then MS likely to detect HPLMN cells.
3) Or the MS timer wont impact for non-registered or even registered MCC/MNC in EF PLMNsel being barred..
You give good suggestion to set the backstop to -110dBm. What if VPLMN neighbours do the same? Will you get ping-pong?
You also say tell subs to manually select. This good idea too, but subs get angry if they have constantly manually select, particularly if manually select is permanently required where they “live” or “work” because the subs are near the border of VPLMN.
I can see alot of MS battery drain going on and re-charging needed.
In border cases – either operators agree roaming agreement costs or they create a regional IMSIs/TMSIs database where MSC bars calls for subs on or near border VPLMN networks.
It would be useful if jean says how many subs involved with his problem?