I've found it can be one of three things (there might be more but these are the ones I've found)
1. (Animation Glitch): As stated above, an odd frame in the animation, it seems to vary exactly what the cause and cure it, here's a few things I've done to fix animation issues in the past:
- A. Add an extra frame at the end, don't call this frame in the FPE, just leave it as an extra frame.
- B. Add an extra frame at the beginning, start your animations at 1 instead of 0.
- C. Add a blank frame in between the open and close frames, don't call it in the FPE just leave it blank.
2. (Texture Glitch): I've found that if you don't leave enough space around your texture islands the ambient system can overlap and cause single frame glitches like this.
3. (Object Spacing): I've found that if you create a door by using two separate objects in one model (ie door and frame), and you place the models flush together GG sometimes interoperates them as overlapping and the animation makes them occlude for a quick second (sometimes completely, I had a door that disappeared when closed which was caused by this), try to leaves enough space between objects so that they're not flush or won't overlap when animating.
Usually if I do all three of these from the start I don't get animation glitches.
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