Key fob losing sync

Hi guys
My original key (key2) was absolutely fine before a long layoff then the batteries must have died. I put in new batteries works ok tries it in 3days nothing not even a red light! Anyways I send it of for repair and a new back. Came back perfect red light works worked excellent after sync. 2 days later it's lost sync. I resync using eka 2 days no sync. I have another replacement key 1 that works everytime never loses sync.
Any ideas. I suppose as a spare it's alrigjt but a real nuisance.
Cheers jb

I have been reading with interest a thread over on fullfatrr ref keys being lost/losing synch. there is a chap called Lukie over there who might be able to help if no-one here can.

I think each fob is supposed to have a rolling code that increments but 1 after each successful unlock and sync in the ignition. So if you use a cloned key it knocks the original out by however many times you used the clone. Only other reason I can think of a key losing sync is not picking up the code from RF receiver (unplugged) or memory chip is losing the code. @martyuk or @MrSporty or @Rick-the-Pick would know more.

Key fob can only be synced after EKA code has been accepted. Entering EKA code does not sync fob.

I must be a bit confused about the procedure. But I can input the eka then sync the key(pushing button ) engine starts no problems. I can then keep opening and closing doors with key 1 then key2 as much as I want. Leave it 2 days then the repaired key loses sync but the replacement land Rover key works fine. These things are really annoying tbh. I think over reliance on electronics that go obselete is just the manufacturers building in obselessence.

There does seem to be a lot of posts regarding failed key fobs just lately. I had a rover that needed the fob batteries changing every month, I used to keep spare batteries in the glove box. The fob for my 2003 Suzuki GSXR still has its original battery and works fine.

Col