Hi
I have the 8" LX90, I think there is virtually no play in Alt or DEC. I'll confirm tonight.
I think the worm may be adjusted, and I think it is fairly accessible, my guess would be that has come loose over time. Hopefully it hasn't too badly.
I found that the DEC knob sometimes came loose as the night became cooler, so I fitted an ez-clutch kit from Peterson Engineering (link below), no issue since.
Philip
https://petersonengineering.com/ez-clutch/