A few trailed frames.
If the problem appears in isolated frames, reject them and keep the clean part of the session.
Why are my Seestar stars trailing?
Trailing stars are not one single problem. They can be a few damaged frames, a windy window, a tracking pattern, field rotation, vibration or a whole-session quality issue. The first step is to locate the pattern.
A bad time window.
If trailing appears in a time block, check wind, mount settling, target position, vibration and transparency changes.
The whole session is affected.
If most frames trail, stacking will not rescue detail. Use the analysis to decide whether the session is worth processing.
Practical rule
Do not judge trailing from one preview.
Judge the session as a dataset. A good analysis workflow tells you whether the problem is a moment, a pattern or the defining quality of the night.