grp52

Assuming you've done the check for signal interference, I think we're down to something's flaky with one or both of the opener's electronics boards. Unless you're knowledgeable of and skilled at PCB board component level inspection and repair, replacement of the PCB board handling the remote functionality would be the next thing to try assuming you can even find a new replacement PCB for your 25 year old opener.

Might be time to consider replacing your opener with a new one.

If you do go for a replacement, remember your ES's Homelink is capable of two way communication with compatible openers to show garage door opening and closing status on indicator lights in the rear view mirror (See page 299 of the 2024 LEXUS ES300H OWNER'S MANUAL USA AND CANADA ONLY.)

Some garage door openers available now have bells and whistles that weren't available 25 or so years ago when you bought you're present garage door opener. Some have interference free LED lights built in, myQ with Wi-Fi connectivity so you can check the garage door open/close status as well as open and close it from anywhere you have internet access, and if you add a wireless keypad remote temporary PIN codes to enable "in garage" package delivery from delivery services that support that which can thwart any neighborhood porch pirate package thieves you may have.

NoiseFree

Thanks I bit the bullet and have ordered a Chamberlain replacement opener.

hotwings

When my trusty 1994 opener's receiver failed I fixed it with this
It simply wires in parallel to the existing wired switches and externally replaces the old receiver.

NoiseFree

It looks cool. How does it connect to your existing door opener and talk to it?

grp52

The LiftMaster 850LM Instruction Sheet - English, French, Spanish (small pdf download) shows how to wire it into your opener's wired control wiring connection.

Programming a remote to the LiftMaster 850LM is pretty similar to programming any Chamberlain Group Homelink capable opening device except there's thee learn buttons - one learn button for each of the three remote channels the LiftMaster 850LM supports.

You can wire it up so that each channel controls a different opener device. Or, if you need to support a lot of remotes (think gated entry into apartment complexes or gated employee parking areas) you can wire it up for all three channels controlling just one opener device.

Once you've got the LiftMaster 850LM wired into your opener device(s) and remotes programmed into the channel(s) used for remote controlling your device(s), it works no different than you're used to with your opener (when your remotes were reliably working).