Indeed looks like persistent engine trouble.
Sailed St Petersburg midnight 17-18/2, but made first brief stop west of Kronshtadt, then again later on 18/2 and stayed anchored until 22/2. Setting off again, she briefly stopped again 23/2 in Gulf of Finland SW of Kotka, and then again on 24/2 SE of Hanko. When proceeding she has only been making 7-8 knots. Then anchored midnight 26-27/2 off Copenhagen.
Today on the move and now south of Trelleborg heading for Gdansk, still at only 7kn. ETA 0300UTC 10/3.