Taking both pictures, exporting all layers as TGA (PNG includes a timestamp so identical images would produce different files), then taking the MD5 of each file for easy comparison:
So you have several clusters of files where the image is the same which is why you have this choppy animation. To be accurate you have two 5-frames breaks:
And of course, I find these identical frames in the pre-animation version your posted. But I still have a very hard time believing that this would be due to the version of Gimp... Do you have the same problem with different steps (-4,-5,-6,-12)?
Code:
0981e9b9c99ce32ba7f0fa516792240a 09-Bubbles-Hang.tga
14a498cd0891c46775ddc1f538111aa9 07-Bubbles-Hang.tga
211d1cd0e80f57ceb8f61bacd525c91f 20-Bubbles-Good.tga
222cbc680d1721821baadefae4125da8 08-Bubbles-Hang.tga
2277462fd382d3b5f958759c81cfe991 23-Bubbles-Hang.tga
22b82ca4f07f70bb6e4f54c03c4a0af0 22-Bubbles-Hang.tga
25d86d9b715ec0a51eacd6ac88ddfeb4 19-Bubbles-Good.tga
25eaac3f2c64e3d288ea3a4aa2bb04b3 16-Bubbles-Good.tga
28668af46bc1500e3c2a2dc155898fd3 18-Bubbles-Good.tga
3aa4363ad8574fcf0ff37515365364c9 06-Bubbles-Hang.tga
3fea529f6ddbf97b70c6b2b42fb538e3 03-Bubbles-Good.tga
4044e71b8a4c944eaa3f559cd889f43a 05-Bubbles-Hang.tga
44627b1c64a6d7f53c76623760939816 06-Bubbles-Good.tga
4f27f0055600bf7a405ec74c7514cf14 10-Bubbles-Hang.tga
5495126d0eaf5f0261e8cc5adf71b275 27-Bubbles-Hang.tga
5a7a40de36d62d8ecc4bd3d0d3cbaf75 25-Bubbles-Hang.tga
5fe3e6240132d1cad6c607b1320c3862 28-Bubbles-Good.tga
602b1c1adb7f7a801dcfe57f7205602c 23-Bubbles-Good.tga
6352efd8e1a04084fb1198fbb6d42226 21-Bubbles-Good.tga
71dc847b20fbd1a98407e7b77352be24 26-Bubbles-Good.tga
784d430f1281a38239711ed46d12bf15 01-Bubbles-Good.tga
7a5225d5446b896fc8ab682c2de1a2ba 13-Bubbles-Good.tga
80a23d8a245af40f7943d6bd5e66c8dc 12-Bubbles-Hang.tga
82b06ae8bfa37a0c3cbfc34e5c75a64b 01-Bubbles-Hang.tga
82b06ae8bfa37a0c3cbfc34e5c75a64b 02-Bubbles-Hang.tga
82b06ae8bfa37a0c3cbfc34e5c75a64b 03-Bubbles-Hang.tga
82b06ae8bfa37a0c3cbfc34e5c75a64b 14-Bubbles-Hang.tga
82b06ae8bfa37a0c3cbfc34e5c75a64b 15-Bubbles-Hang.tga
82b06ae8bfa37a0c3cbfc34e5c75a64b 16-Bubbles-Hang.tga
82b06ae8bfa37a0c3cbfc34e5c75a64b 17-Bubbles-Hang.tga
82b06ae8bfa37a0c3cbfc34e5c75a64b 18-Bubbles-Hang.tga
82b06ae8bfa37a0c3cbfc34e5c75a64b 29-Bubbles-Hang.tga
82b06ae8bfa37a0c3cbfc34e5c75a64b 30-Bubbles-Hang.tga
83ca2c93ce356566c222a11da678bf4d 17-Bubbles-Good.tga
84ffdb2d336c31e6b572c4f3c481248e 08-Bubbles-Good.tga
89b9f28ab1d42c4e1e6faf448f2c52b5 21-Bubbles-Hang.tga
89c1bb5a2e62a1b61c83e55e36b11e7e 29-Bubbles-Good.tga
8a3563aab091466e89b3cb4bca958fbc 15-Bubbles-Good.tga
8dd10c57464fb43a6d82769e7464f451 14-Bubbles-Good.tga
8e9fa09ea20dcdc6f7184067ac9ca20f 26-Bubbles-Hang.tga
93a124d77710a832278b9ad7e6f58a54 27-Bubbles-Good.tga
99bb216a0b47e27e3ed85e9528e974c6 22-Bubbles-Good.tga
9ef8723e92cd2f2259e46fd2f213e518 24-Bubbles-Hang.tga
b67178f5cf6703d56e68a5590582445d 11-Bubbles-Good.tga
b87fdc07fcf0b3300a953f468a41cdbd 09-Bubbles-Good.tga
be62c80f378ff1c6bac5b5d4f63e3eed 12-Bubbles-Good.tga
c0308625397211d689a6123e1c53481a 30-Bubbles-Good.tga
c1b58be3d9423a1248e1df7a285f08e9 04-Bubbles-Good.tga
c5c1a9fe6e30e9eba7c3921791956864 02-Bubbles-Good.tga
c7052aa6d96d59c4e85cf0291aea7663 13-Bubbles-Hang.tga
d0db97ecbdf742fc13e4f63e709cb979 19-Bubbles-Hang.tga
d17f0b67e8d82dbebf1ff8d1f6c06db7 28-Bubbles-Hang.tga
d43d58cd973e39ef4e29734d629fae7d 07-Bubbles-Good.tga
e11f28f3b91daa8536fdad36c68fa8be 05-Bubbles-Good.tga
e1d7e0dccd9e66d01cd4a737b6861559 24-Bubbles-Good.tga
e2d27aeae44653280dbb03f9a01a0632 04-Bubbles-Hang.tga
f2c363c2ab875b2038877cca87d3fb97 20-Bubbles-Hang.tga
f7f2bc2c35f0f6f863c5ffe065f8ad82 25-Bubbles-Good.tga
fabe2134607ee1de35ac3c70c55f3473 11-Bubbles-Hang.tga
ff1a4d1ffc951ca8475fa6696507d750 10-Bubbles-Good.tga
- 14-15-16-17-18
- 29-30-01-02-03
And of course, I find these identical frames in the pre-animation version your posted. But I still have a very hard time believing that this would be due to the version of Gimp... Do you have the same problem with different steps (-4,-5,-6,-12)?