Thx for advice @sebi.zzr but not much to add.
OS Windows 10 64bit. Tried both newest KSP release 32bit and 64bit clean install of
Kerbal Inventory System and Kerbal Attachment System and is still same
problem. I've asked mod owner and they replied:
Quote from ihsoft >>
Such issues are usually mods conflict consequences. Please, try removing all other mods and re-test the issue. If it's gone then the next step is determining which mod causes the troubles. As of now there are no known mod incompatibile with KIS.
Also, consider registering on the KSP forum and reproting the issue there. There are many poeple who may help with advice.