SLD File Documentation 100%?

I was looking through the openage SLD documentation here

https://github.com/SFTtech/openage/blob/master/doc/media/sld-files.md

and the SLD Extractor which seems to follow it here:

https://sld.aoe2.se/

I think the implementation with duplicated blocks from the previous frame is slightly incorrect, and this could mean the documentation might be slightly wrong? Although I can't work out exactly how.

On some of the sprites (ones with portions which are static for several frames) the algorithm also incorrectly copies blocks elsewhere - see the war wagon death animation:

It seems a lot of the blocks from the collapsed wagon are correctly copied from the previous frame (because they're not moving) but then also blocks by the horse's head are also being incorrectly copied.

If any of the openage community could help me in understanding why this could be the case, i'd be able to update the SLD Extraction JS code and fix it so it's perfect. I'm sure there is a rule that might not be documented or something...

Many thanks!

Start with doc/media/sld-files.md and compare its duplicated-block description with the SLD Extractor at https://sld.aoe2.se/. Reproduce the war wagon death animation case shown in the issue, determine the rule governing copied blocks, and document the rule or identify the required SLD Extraction JS correction.