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Yea that's definitely tricky. I'm assuming you haven't taken out any load balancing that was previously in place between desktop and m. meaning your server is struggling a lot more? The Page Speed Insights tool can be good info but if possible I'd have a look at that user experience index to get an idea of how other users are experiencing the site. A next port of call could be your server logs? Do you have any other subdomains which are performing differently in search console? In terms of getting Google to crawl more, unfortunately at this point my instinct would be to keep trying to optimise the site to make it as crawl-friendly as possible and wait for Google to start crawling more. It does look like the original spike in time spent downloading has subsided a bit but it's still higher than it was. Without doing the maths, given that pages crawled and kilobytes downloaded have dropped, the level of slowdown may have persisted and the drop in that graph could have been caused by Google easing back. I'd keep working on making the site as efficient and consistent as possible and try to get that line tracking lower as an immediate tactic.