Minecraft player keeps bagging himself back?

A friend of mine now has a "new" pc of a slightly older model and we wanted to play Minecraft. Everything was also fluid, but she always pulled herself back a little and was therefore banned for 10 days for "hacking". We then tried it on the version that we had previously played with your old pc on the 1.8.8, but the same problem occurred, is it the pc or Minecraft?

Are other players working?

Yes, all other players move normally

That may well be due to the internet.

Now the internet works pretty well for her. I don't know why that is suddenly the problem, otherwise everything runs smoothly

This can also be due to the server that the server is bugging. Among other things, if the server is overcrowded or its capacity is overloaded.

Games *

That could be a possibility but it has never been the case before

Hm if you said it is an older pc then it is probably the pc.

It's up to Minecraft!
Which server do you use?
If it's something like aternos or minehut (* gag *) you don't have enough ram.
But you said banned, so it is more the server. Writing to support is the best solution.