The Funny‐looking Obstacle

After the shared sections in the first two messages (East 1 and West 1), there is an alternating section of aligned and misaligned trigrams, with 4 different, 4 the same, 4 different, and then 13 the same, with 9 inside this last segment of 13 (ending right before the last shared trigram) being an occurrence of the main isomorph which occurs 6 times in the first 3 messages, with the same ciphertext sequence in both of these messages. We call this section of alternating synchronizations (particularly the parts of it that are desynced) the funny-looking obstacle.

This is likely caused by two short words or fragments of words (of about 4 letters) being swapped in these two messages, with a shared 4-letter segment between them. E.g. it could be something like EAST INTO WEST/WEST INTO EAST (ignoring spaces), or EAST TO WEST/WEST TO EAST (including spaces), or something like COPPER+[FROZEN...]/SILVER+[MOLTEN...] (though I know these do not exist as actual material tags).

This feature has been demonstrated to be possible to reproduce with deck ciphers, both with and without the second 4-letter misaligned segment being different text in the two messages. The first misaligned segment needs to be different text due to a perfect isomorphism conflict.