We had that problem one time when we first started out, and switching to Thetford TP prevented future issues.
If you are not limited by water, and have sewer connection at site, I think I would start with lots of water (maybe half a tank) to test whether that solves the problem, and if it works, then gradually reduce the amount.
In any case I would buy toilet paper that dissolves quickly. Not all brands are equal even if made for RVs. You may want to test some yourself.
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