Grigoriopol-Mayak: I have followed them fairly regularly and I have noticed only those two longer outages for 1413 and 999 kHz. The first time the break was in the morning and then also 621 kHz went off. The second time it started after 1700 and then also 1548 kHz was off.
They can be heard with good signal here in Finland during darkness hours and even at daytime on carrier level. If there is any specific day in the past that interests you, I can check TOH recordings.
At the moment both 999 and 1413 kHz are on the air, 999 kHz stronger.

Mauno Ritola, MWlist iog (2022-05-11)