Created attachment 4242 [details] screenshot of grayed-out box When a subscription is Irregular, we cannot change the status of new issues we receive because the status box is grayed out on the Serial Edition page. Evidently this didn't happen in 3.0.x. We can workaround it by giving the serial a fake periodicity but that seems inelegant.
The behaviour of the irregular frequency changed with the serials frequencies rewrite. I can't reproduce the problem on current master. The version this was reported against is no longer maintained. Please reopen, if this bug still appears in later versions of Koha.