Additionally, you have quite a few foul prone players. That can exacerbate the problem of playing with weaker inside defence and rebounding. The two are likely mutually inclusive.
Salehi, Slegt, Kaasma, Mittner, Castureddu, Stroz, Jaderholm foul at pretty high rates. Comparing bigs and smalls might not work, but if you look at Salehi and Jaderholm, they foul 3.2 times per 30 minutes and your guard Rebins fouls 0.7 per 30 minutes. That has to mean something.
M2M is the tactic I'd use. If you can slow the pace (e.g. motion instead of run 'n gun) without skipping the beat, that's a start.