How to minimize midi stuck notes

Good morning

I’m getting a lot of stuck midi notes in a session using two instances of sfizz

Both instances are loaded with virtual playing orchestra instruments and playing monophonic lines.

In the session I also have one instance each of Sitala, SetBFree and general midi synth
The rest of the tracks are pure audio. It is only sfizz that gets stuck notes in this session.

I am running at 48KHz and have a buffer size of 1024. the dsp is less than 20%. Changing the buffer to 2048 doesnt seem to make any difference to the frequency of stuck notes.

Sfizz lv2 seems to be the least DSP hungry and most stable sampler on my system.
I made sure that none of the parts gets to close (< 1/4 note) to the end of its containing region.

My system is Ardour 8.12 on Debian Trixie, which is tuned up as to x42’s advice on the forum.
Can you give me any tips to reduce the note sticking?

Many thanks