I highly suggest you watch the video above and others like it. You need a better understanding of the parts and what they really do before randomly wrenching on parts. It leads to mistakes and frustration that don’t solve the real issues.
- It would never “work” with the goal you had in mind.
- This fastener is the “pinch” point that only secures the cable to the derailleur. It is set at the beginning of the derailleur setup and should not be touched after that moment.
- It does absolutely nothing specifically for adjusting the “tension” of the cable. So “over” tightening it would have no affect other than potentially stripping the fastener and smooshing the cable more.
- This adjustment is the “right” one to look at in most cases. Adjustments should be done in a deliberate direction (tight or loose) in accordance with review of the result from making a single shift (up or down).
- It’s a bad idea to randomly turn the adjuster without a clear understanding of the direction of adjustment and the expected result.
- Turn it no more than a 1/2 turn and then retest shifting performance in both directions.
- This all leads to what I think is needed, a reset.
- What exact shifting and gearing (10-speed, 11-speed) do you have on your bike?
- What exact cassette is installed on your trainer?
- Is either one (trainer cassette or drivetrain on your bike) very old and possibly worn?
I can’t help but think you may have a mismatch of some sort (speeds or wear) that is the primary issue that is not being addressed.