For the time being I have not had any issues with any combiner connectors.

I used to play with the three Energon combiners and have kept them on display in gestalt mode for 5-6 years. ROTF Bruticus and TFCC Nexus Prime has been transformed a few times but ROTF Superion is still sealed (not for long). I'm visiting home this weekend, so I'll try to dig them out of storage to see if there's any busted translucent parts. I'll be more worried about the repaints - risk from mould degradation and the cost of replacement.

From memory, the exact type of translucent plastic used in Energon was quite tough (as opposed to Animated Stealth Lockdown). I used to play with the Autobot powerlinx deluxes all the time.

Someone has designed Energon connector plugs from Energon to PCC. However the same maker/seller has not made replacement Energon plugs on their own. If you need to replace the translucent plugs, it may be easier to buy a cheap Energon Deluxe squad leader and take apart the connectors.