KAKU not reacting on RF-link

[najtram]

I have an issue with my KAKU (COCO) lights. (so it is actually not an RFLink issue).
Using RFLink I cant switch the lights (any more), with a remote I can, but only when I'm really close to the KAKU (1cm). With that same remote I can switch other lights with no problem, so it's not a strength of signal send issue. With RFlink I can also switch the other lights.
Strangely this issue occurs with two, same devices: both ACM 300.

So somehow it looks like an age thing of the devices, does someone has any experience with KAKU getting older and having more difficulties in receiving signals over time?