Mapi… may be ashamed of it. Especially the sequences are saved in memory inaccessible to the user (unless you have root). Apparently, for privacy reasons, you should send photos to blurred first (according to them 
, and not try to copy files first) …
For me, the sequences are saved in [/data/user/0/com.mapillary …].
Go to Settings → Developer (and here the Save debug logs to file option, shows the location of the files). if you don’t have root, it won’t help you anyway.