Ajax output calculation fails in version 4.0

[tzcccc]

Classes/Ajax.php line 89 from version 4.0 running on TYPO3 8.7.30 php 7.1.33

$queryBuilder->resetQueryParts(); seems not to work as expected
Next query output delivers only one record. If replaced with new instance
$queryBuilder = GeneralUtility::makeInstance(ConnectionPool::class)->getQueryBuilderForTable('tx_contentrating_rates');
all relevant records will be fetched.

In this case calculation fails as $this->rate_count = 1 and $this->rate_temp1 < 5
Output is always < 25 %