If the symptoms only
occur when in a browser, then the cause would presumably/probably be in either a feature of the browser (but I have never seen such a feature as that as a default feature of a browser) or (and more likely) a feature of an extension/add-on.
Given that PaleMoon is a Mozilla-derived browser and SeaMonkey grew from the Mozilla Application Suite, I would suspect that a common extension/add-on (one that you are using in both browsers) is producing the symptoms - by design rather than by accident (i.e., it is probably not a bug).
What you should probably do is look through the extensions/add-ons and their settings in one
of the browsers, to see if you can spot the likely culprit.If that doesn't throw up any suspects, then try a process of elimination:
- Disable (do not delete) half of the extensions/add-ons in that browser.
- If the symptoms persist after you have restarted the browser, then re-enable the previously-disabled extensions/add-ons, and disable the other half.
- On restarting, the symptoms should have gone away.
- When the symptoms have gone away, you then re-enable the disabled extensions/add-ons, a few at a time, restarting the browser each time and checking to see if the symptoms have returned.
- When the symptoms do return (as they must, eventually), then the last few you re-enabled, as a set, must contain the problem, so you then disable all but the first in that set, restart the browser and keep that up- re-enabling them one at a time - until you identify the single problem extension/add-on that produces the symptoms.
Tedious, but pragmatic and it should eventually identify the causal problem extension/add-on.
Hope that all makes sense and is of use.