Big issue with data repeatability - position error over 10cm

Some NTRIP providers send messages that some receivers can’t read.
I had the same situation with Topcon ntrip service in Greece.
When I used the VRS mountpoint all the points had 10cm offset vertically.
The rover was a Hemisphere brand but the same situation happened with DJI Mavic 3 Enterprise RTK.
So it is crucial to use your own base station to avoid such problems.
I use my Emlid M2 as base station and send corrections via Emlid Caster or in Local Ntrip if there is no cell coverage.
The other day I had a bad fix on the base station and it was 30cm off. The Hemisphere had good repeatability but the Emlid struggled to have a good fix in the same point. The base station was 18km away, not that far.
Anyway after some attempts the base station fixed closer to the Hemisphere point XYZ but again it had 6cm horizontal error.
I don’t know why this happened but in the past I had similar situations mainly in remote areas away from the ntrip base station.
I guess we can’t have it all in a affordable product.