We have a 1GB Cloudways server where there is only 1 live and 1 staging site, both have access to 512MB, however, when I try to import about 100 xliffs, the site always ends up in 502 Bad Gateway. I have split the zip into 2 zips, no success, I have now even split is up into 4 zips with 25 xliffs. The first import worked, the second resulted in a 502. I have installed WP Memory which shows 512MB available, and only 9MB in use
Solution: upload the XLIFF files in smaller batches of about 10 or so. Also make sure the pages were downloaded in the same job, otherwise the job IDs will not match and the translation will not be applied.