Did you tried to replace the Power Supply / PSU ? As you have a "general" problem, it could be due to such problem like low Amp due to old PSU... or something else on the hardware starting to have some issues.

For the latest image it works good, naturally as always new modifications are done by OpenPLi Team that could get the skins failing. So you should try it without changing skin and see if goes ok, and naturally flash from zero the box, assure yourself there is enough flash memory avaible as well. Concenring the Channel list, sometimes it could be get corrupted as well... so time to time a full scan of the satellites is recommended.

Concerning the Sim, put it on another MIPS box you have (like other DM800HDseV2 etc) on frontpanel (like a Pay-Tv sub card), and run the JAM Plugin (Japhar Support), at the end of the list there is the Japhar FrontPanel programming (using the frontpanel to reprogram the "failing" sim)... to the model of box you need. That way is more straight and could avoid any failure/risks.

TS