i’m amazed at one thing : your bosses are pressuring you, and you just have to spend 5 minutes reading the 3GPP specs to find an answer…
and you didn’t do it.
so ok, i did it.
the 3GPP 22.811 is not relevant to your case, it applies to non_3GPP reselection.
but if you look at 3GPP 23.122, you will read this :
22.214.171.124 In VPLMN
126.96.36.199.1 Automatic and manual network selection modes
If the MS is in a VPLMN, the MS shall periodically attempt to obtain service on its HPLMN (if the EHPLMN list is not present or is empty) or one of its EHPLMNs (if the EHPLMN list is present) or a higher priority PLMN/access technology combinations listed in “user controlled PLMN selector” or “operator controlled PLMN selector” by scanning in accordance with the requirements that are applicable to i), ii) and iii) as defined in the Automatic Network Selection Mode in subclause 188.8.131.52.1. In the case that the mobile has a stored “Equivalent PLMNs” list the mobile shall only select a PLMN if it is of a higher priority than those of the same country as the current serving PLMN which are stored in the “Equivalent PLMNs” list. For this purpose, a value T minutes may be stored in the SIM, T is either in the range 6 minutes to 8 hours in 6 minute steps or it indicates that no periodic attempts shall be made. If no value is stored in the SIM, a default value of 60 minutes is used.
in other words, the MS is reattempting to reselect the HPLMN every hour, by default.
read it more in details, because i just read it quickly….