apostolakisl

You have to have the old switch in the root folder.  So first right click and remove from folder, then go to its new location in the tree and right click and you will see the "replace with" command.  The new switch will have to be the same switch or an updated version of the same switch or you won't be given the option to select it as the destination of the programming.  

I have suffered the same issue.   First off, there are some revisions of the current firmware that supposedly fix this bug. Go to https://polisy.local:8443/WEB/sysconfig.txt and find your current firmware.  You will see a section that looks like this:
isy-5.7.0_5 Name : isy Version : 5.7.0_5 Installed on : Thu Oct 26 20:04:26 2023 CDT Origin : misc/isy Architecture : FreeBSD:13:amd64 Prefix : /usr/local Categories : misc Licenses : Maintainer : michel@universal-devices.com WWW : UNKNOWN Comment : ISY Port to X (IoX)  
The latest version is 7..5.0_5   My system was on the _4 version when it spontaneously disabled all my programs.  Please do an "update packages" to get the _5 version which I pray fixes the issue.    
I am going to assume you have programs that are supposed to be disabled and that you have lots of programs and that figuring out which ones are supposed to be disabled would be a major PITA.  In that case, hopefully you have a recent backup so you can restore the programs to proper enabled/disabled status.  If it is easy for you to know which programs are supposed to be disabled, just go to the program summary page, block highlight all the programs, right click, and click enable. 
Unfortunately, my backup was 6 months old and my system had changed.  First I made a current backup of the system.  Then I restored my 6 mo old backup, took screen shots of all the programs showing enabled/disabled, then loaded the current backup back onto the system.  I block highlighted all the programs and enabled them, then went back and disabled the 30 or so that needed to be disabled using my screenshots.  Then I made a new backup just in case _5 version hasn't actually fixed the issue.
 
 

@photogeek54 The Elk module for ISY I suspect is an EOL product.  If the new Elk isn't identical to the old regarding integration, the Elk module won't work and UD is not doing any module development.  They even threatened to stop native Insteon support (but they backed off on that).  As far as I know, only zwave and Insteon will continue to have native support on the UD consumer products.  Everything else will go to a node server.
I had the module when I had my 994i.  I have switched to ISY on Polisy which does not support any modules, so I had to switch to the node server.  The node server by @Jimbo.Automates is better in that it integrates more Elk features, but it is worse in that it doesn't present and organize as well as the module.  For example, you can't click on a tab and see all your zones, voltages, and status in a nice table all at once.   Or all your outputs in a single table along with status.  Things are just in folder trees, somewhat mixed together and you can only view the status of one at a time by clicking on it.  I don't believe that there is anything @Jimbo.Automates can do within the confines of a node server to change that.
 

Those old dimmers I had failures.  The newer dual band ones I have never had a failure that I can recall.  I decommissioned my entire single band setup years ago and replaced it with all dual band.  I was able to fix a number of those older ones by replacing the capacitors.  But I don't recall ever having one behave like you are describing.  To open the switches, however, you have to drill out the rivet on the heat sink.  When re-assembling, you need to have a rivet set.