Signal strength in RMS is discontinuos

Hi, in RUT955 with software versions at least from .16 to .19 the signal strength metrics is not continuos, but has holes (see picture).
This happens in RUT955 routers with RUT9_R_00.07.06.19 and latest modem firmware, only (as far as I’ve seen) for modem Meiglink SLM750-VE. But it happens even with the latest modem version installed.