Manually editting stock does not save stock

Hi,

When manually editting the stock on the “wp-admin/admin.php?page=stock-manager” and clicking ‘save’ or ‘save all’ the stock is not saved. On refreshing the page the old stock is displayed again in the stock field.

No errors are shown in PHP’s error log and memory limit, post max size and max input vars have been massively increased without succes.

Please advise.