Is there something wrong with my 4-Slot?

I have a 4-Slot in a cab, if I leave it on for more than 3 hours, it tends to overheats and then the sound doesn't work. But once it cools down it works again.

Does anyone else have this problem?

Is there any way, I can fix this?

In answer to the question in the topic, yes!

Well where abouts is the board? Does it have plenty of room for ventilation? Is it near the PSU?

You could always put a fan in, but this isn't really something generally done to cabs. Fit better heat sinks to the chips/transistors that are overheating.

Yeah over time, the inside of the cab gets extremely HOT. Maybe I should leave the cabinet's door open from now on for more ventilation.