Mk161 programming loss

Hello, I have 4 2 channel infrared receivers (mk161). They were assembled last year at about this time.Two were programed and used to remote control the grandkids Christmas train.They operated last year without trouble.When they were set up this year they worked fine.The second train was finished this year and worked fine.These trains are on 2 separate tracks with 2 identical and separate power suppies .The tracks are hot all the time.All 4 receivers lost the user programing while sitting idle. Hope you can help. Thanks, Rich

Sorry, but this highly unlikely.
Data retention is typical 40 years.
Unless they have been struck by lightning or a power surge, they should keep their memory.
Either they have been accidentally put to learn mode, or the code in the transmitter has been altered.
Please check this.

Thanks for your response.The transmitter is a K8049.I reprogramed the first train and it’s working.I have not done the second as yet because of the level of disassembly required.I was surprised at the loss of memory because of the long life of eprom programs.The transmitter is not reprogramable or is it (without disassembly).The fingers of a 9 year old can do some impossible things. Thanks again Rich

You can download the assembly instruction for the K8049 (link below)
Page 10 will show the modes.
Looks like you need mode 4

Thanks again, Rich