When I was reading the code, I noticed that

The brackets are redundant in __txn_fixup_prepared_update

else {
        WT_ERR(hs_cursor->remove(hs_cursor));
    }

and it should be remove instead of insert in curhs_remove function:

CURSOR_API_CALL_PREPARE_ALLOWED(cursor, session, insert, CUR2BT(file_cursor));