I have a Lidaldi one that now behaves in the same way. I think I may be partly to blame, as it has a power take-off of 1400W and I have my SCMS connected to it which is somewhat more hungry than that.
Funnily enough, mine started working properly again, for no reason that I could fathom, after being mardy for quite a long time, and it stayed that way, also for quite a long time. It's back to being mardy at the mo.
It will be something failing in the electronics. Probably not difficult to fix if you can get a new circuit board, or have an electronic friend.