If something moves on a rail block, it sets any nearby signal to true.
If it moves away (or undocks), it sets any nearby signal to false.
This change made the rotator block an exception to that rule. It sets any nearby signal to true **after** it's done with the rotation cycle. That doesn't work well since after the rotation cycle it also tries to move it away to the next block.
**What it should do:**
# Send a true signal to nearby blocks when a rail entity moves on the rotator at the **start** of every rotation (even if the rotation is 0 degrees/disabled)
# Send a false signal to nearby blocks when a rail entity moves away from the rotator to another rail, this would happen at the **end** of a rotation cycle (unless it's 0 degrees again)
Even with this fix, 2. doesn't work at all. It doesn't get set to false either by moving it away, or by undocking.