The symptoms are as follows.
- Start X4. At the title screen menu it will report that X4 is not modified (the modified tag not visible).
- Load up a not modified save. The escape menu will report that X4 is not modified (the modified tag is not visible).
- Play normally. Do something that triggers the issue (currently unknown).
- The escape menu will report that X4 is modified in orange.
- Any saves made from now on will be marked as modified, with the modified tag showing in the menu on load.
- Exit to the title screen menu. A warning dialog will appear informing you that X4 has been modified with the modified tag showing in the menu.
- Restarting X4 reverts to step 1, reporting that it is not modified.
To try and find the cause it would be useful to know what can trigger the "modified" tag during gameplay. Starting X4 with third party mods installed obviously triggers the tag, but this modified tag is being added during gameplay. Could it be due to some accidental key combination, possibly used for debugging, since when flying the destroyers I am pressing more keys than normal to change camera, reposition, e.t.c.? Could it be due to a debug or command console like feature that runs on some event accidently leaking into the live build? Or is this caused by some sort of tamper/cheat protection being triggered erroneously?
If the cause cannot be found I would recommend expanding the title screen menu warning dialog feature so that it is also shown during gameplay the instant X4 switches to being "modified" since that would make discovering the cause much easier.