Change destination command as well as some doesn’t work in route

Whenever I go to select a destination for my train In surveyor and driver mode the command turns gray as to where I can select any destination

The command script may be timed out due to how it works. Not knowing how it's written exactly, but to me it sounds like the script searches the whole route for destinations. When commands do that, they cause a major timeout and stutters that cause poor performance. Since TANE came out, scripts that do that, such as Wait for Trigger, are prevented from executing.

If the script can be edited, perhaps someone who is capable of editing the script, and also has permission to repair the asset to do so, can fix the problem.

For maps with a large number of trackmarks and/or industries use the rule <kuid2:206816:99004:4> DestSignTable to disable these as destination signs. Better define your own destinations in the rule.

Peter

Greyed out often means you reached a maximum (N3v often ignores it if we talk about it)
I use Peters wonderful <kuid2:206816:99020:6> Change Destination Sign (MP)
slightly modified with submenu's (or it ran off screen)
have 1295 trackmarks and 60 industries in use as destinations on my main route
you can count them with my Set-Driver-Condition-Rule if you want
greetings GM

I have a lot of trackmarks, I’m almost finish to completing the entire NYC Subway system all 468 subway stations and track marks for all stations and industries for most of them

Whenever I open another route to use the same command it works properly

Like i said you reached a maximum
check if you have "industries" that are not really a destination.
on my route i had to replace 200 "Industry" Windmills, made them simple scenery and commands started to work again