Currently I'm in the same position too after attempting the update for the mech beast on the DMM player also so maybe something went wrong when I was editing the file for the 0_download? Messing with copies right now but no results yet.
For the DMM player, did you manage to to get the Ayakashi Rumble characters' scenes? I haven't needed to modify anything besides 0_download_json, so if the subsequent steps are what's falling I don't have any ideas at the moment.
Edit: To be more specific on the 0_download_json edits:
Replace "resource_code = '/'.join([resource_directory[-4:][i:i+2] for i in range(0, len(resource_directory[-4:]), 2)])" with "resource_code = '/'.join([resource_directory[-6:][i:i+3] for i in range(0, len(resource_directory[-6:]), 3)])" for lines 228, 333, and 427 [-4 is replaced by -6, 2 is replaced by 3]
Replace "for y in xrange(250):" with for "y in xrange(300):" for line 501 [250 is replaced by 300]
Replace "for idx in ((0, 1), (0.011, 35), (0.216, 6), (2, 10), (5, 50), (6, 200), (9.05, 10), (9.2, 20)):" with "for idx in ((0, 1), (0.011, 35), (0.216, 6), (2, 10), (5, 50), (6, 200), (9.05, 10), (9.2, 20), (9.51, 6)):" for line 513 [(9.51, 6) combined with the eidolon ID append command leads to 9511, 9512, 9513, 9514, 9515, and 9516, which are the Machine Beast eidolons' summon_id values, that I found by using them in battle with the Dev Tools open]
On my end currently I'm using the 0_download_json that you posted prior so I'm assuming that these edits are already in place. Currently I did not see any of the ayakashi rumble character scenes.
The error logs aren't that different: you have some Machine Beast eidolon files that didn't download during 1_download_assets, doing that step multiple times might help. I always do it at least twice for clean installs of both the Nutaku and DMM players. I have some errors that you don't relating to downloading extra json files that don't have assets due to experimenting with 0_download_json. I'm worried that one of my setups from before the uploaded edited scripts is what got me the files. Is there anyone here that have gotten the edited scripts to work?
Hmmmm I've tried the 1_download_assets again and it seems to run through the entire thing without pausing to install more files so maybe I might have to delete and redownload the files for the mech beasts?
Okay so following up, I can now see the Akakashi Rumble collab characters now, but it seems like the 1_download_assets keeps skipping the missing files for the mech beasts for some reason.
Let's compare config.ini files. It gets created by the 3_write_config script. You could try backing up your config.ini (cutting and pasting it somewhere else) and put my config.ini where it was (same folder as the scripts). Then run the player and click one of the new character scenes, if any appear.
Edit: I had to split the file into fewer than 6 parts that are less than 97KB each. Then I renamed "config.zip.001", "config.zip.002", "config.zip.003", and "config.zip.004" to "config 001.zip", "config 002.zip", "config 003.zip", and "config 004.zip" since 001, 002, 003, and 004 aren't recognized filetypes.