Master planning / on-hand issue (net requirements)

Has anyone ever had an issue, where on-hand quantity on item net requirements does not match to the actual on-hand? This causes a lot of unnecessary planned orders etc. I have checked positive days, etc., but even outside of positive days, you should be able to see the correct figure on the form.

Here is a screenshot of the problem. Net requirements screen and on-hand screen is from the same item. Dimenions (site, wh) are the same (coverage by wh dimension at dimension group). Screenshot is just after a full master planning run (without any filters), and I have double checked that the plan is the same. Of course all the action and futures messages with cancel are quite a mess at the moment.

Coverage code: Period
Coverage period: 1
Coverage time fence: 124
Negative days: 124
Positive days: 124
Minimum: 0
Fulfill minimum: Today
Minimum periods: False