J2-21 will start only at beginning of the day

Hi,

We have a J2-21 that was ok for a long time, however since last week it will only start in the morning when just switched on. Vacuum isn't great but doesn't seem to matter. If I clean the door seal it will reach into the green area all right, but after the machine has been cooling for a longer time, the start button won't be activated any more so we can no longer do runs for the rest of the day.

Has anyone an idea what this may be?

Thanks very much,

Dick J. Schol

Netherlands