Midi recording fails in loop

When i record a midi phrase in loop, recording sometimes randomly drops out. Here in more detail.
So i’m recording a midi track that plays an external synth, so Cubase basically works as midi loopback. Some other tracks play some audio and some VSTi, some effects also work, but really it’s just a few, this system used to handle way more load and was fine.
So i set up a loop with markers, it’s a lenghy one, like 16 bars or smt, and engage looping in the transport bar and hit record. Its when you play the phrase over and over until it’s perfect. So after practicing like that for three or four loops, suddenly i notice the metronome stops. But the background music from other track continues, and so does that vertical bar on the screen. Then, after this metronome-less take is finished, it comes back on on the next one.
Then, after this happened a couple times, i stopped the recording in the middle of a take, when the metronome dropped out. And this is when i also noticed, that the midi part hadn’t changed from the last take. Meaning that when the metronome stopped, the midi track also stopped taking in notes from me.
It’s Cubase 10.5.