SYL500 forgetting 94335e Remote?

[Padge]

Hi
I have a SLY500 sliding gate kit. The two original remotes supplied with it work fine.
I bought two spare remotes(94335e) They work for a few cycles after I go through the programming procedure. Usually the next morning, the SYL500 has forgotten these new remotes and they no longer work (until I reprogram the unit).

The original units always work.

Any suggestions?

Thanks
P