Hey Roberto!
So I have used Trust bars a bunch mostly 2018-2020 vintage a few older ones too...not sure exactly which part you are referring to? Sounds like maybe the buttons that you press to change bar width, those tend to get sticky after a while, anyway my .02 would be as follows:
#1. If you proceed with trying to repair your old bar - just buy the oldest 2019 part - Trust bars have been the same for quite a while.
#2. Consider NOT doing #1 cause once you start fixing old bar parts there is probably another worn item which pretty quickly adds up to a new or newer used bar.
As we say in my business COST is ONLY an issue in the ABSENCE of VALUE - I get saving a few bucks but IMHO your bar & lines is NOT the place to economize. Many of us will BUY new bars / lines every year or two at most cause we kinda like not dying - hence, lots of decent bars out there even on the pre-owned market. Also lots of leaps forward in line tech vs. the old white frayed ones. You might be surprised how much VALUE you get out a nice SK99 line set.
Good winds :/
Mc