Midi clock drifts and timing issues

Hello ,

im using Cubase 9.5 updated to last version available with RME HDSP-Aio allso with updated drivers .
synths - SH101+ tubbutec midi kit conected through the RME midi in\out ports sending midi clock from cubase to those ports through “project sync page”
the timing always has unstable issues and after few bars its getting off sync . same thing happends with MS20 classic connected to Beatstep Pro via cv\trig ins from the MS20 to the Beatstep Pro CV\GATE outs and from Beatstep Pro USB to my PC in order to get sync from Cubase. same thing here the bpm drifts for example my project is 145 BPM when i’ll play it the Beatstep Pro clock jumps from 145 to 144,142,146,145 and does not getting any solid timings . i tried to eliminate each instrument by itself in order to see if the problem comes from 1 of my other stuff but even if its only 1 instrument connected it still not stable with timings . tried to get cubase “use external clock” from Beatstep Pro but cant get it to work . any solotions ?

after 2 days of furstrating reasearch across the net trying to understand the base of the problem i have finaly came a cross to the solution that solved my clock drifts . the solution for that is to cheack\uncheack “use system timestamp” inside Cubase under: studio > midi port setup , bellow the midi port table cheack or uncheack (depands on your system just leave the 1 that overcome the drifts and the clock stays on time)