A few things
- first, at very short distances it is possible that the the router is overloading the input of your phone hence causing the loss or corruption of the data.
- second, any loss of connection can result in the sort of symptoms you are seeing, breaks in the download (or upload) resulting in the message "waiting for download". BOINC is designed to go into a series of successively longer delays until such time as the communications link improves and so proper communication (download & upload) can be restored to some form of normality.

Asteroids is another story, their server is sending but not receiving.... (has been like that for a week)

11/07/2020 20:01:59 | Asteroids@home | [error] Error reported by file upload server: can't open log file '../log_project1/file_upload_handler.log' (errno: 9)

Absentee Administrator syndrome. Until a tecchie sorts out that log file, nothing will get through - no point in retrying.

The WiFi RF stages on phones are often not as well designed as other devices when it comes to very high signal strengths - one of my old phones used to drop it's entire RX capability in very high RF fields - annoying when working near airport radar systems....

Hitting the download retry can often trigger a good connection, so no surprise with what you've observed.

Asteroids is "well borked" just now, and the system administrator doesn't appear to be reading or responding to either his PMs or the message boards - there's quite a heated debate going on over there, and has been for a couple of days.

The WiFi RF stages on phones are often not as well designed as other devices when it comes to very high signal strengths - one of my old phones used to drop it's entire RX capability in very high RF fields - annoying when working near airport radar systems....

Not just phones. That probably explains why my DAB car radio always cuts out just as I pass the highest point on my route out to the south-east - a hill crowned by several transmitter antenna towers.

Strange, as my cheaper phone is ok with it. One was £20 and the other is £40. Good specs though for that price - the £40 one has a 720p 5.5" screen with gorilla glass, a quad core ARM Cortex A53 CPU @ 1.25GHz, 3GB RAM and 32GB storage, running Android 7.0. The camera sux, but don't they all? It is true that it works better further away from the router, whether it's the phone or router that's moved (I spent ages trying to find out what other devices in the room were causing interference!) But since I changed the router to use a lower speed for Wifi (which may also reduce the power?) it connects almost all the time.

RF design in phones is always a compromise, and even within one manufacturer the RF performance varies quite substantially - think back to the troubles Apple had with one of its iPhone models when they got the layout of the antenna wrong. Price, processor, memory, operating system etc. are absolutely no guide to RF performance.
RF swamping can be partially eliminated by reducing the data rate - I doubt that it reduces the absolute power from the router, what it does do is increase the power/byte, thus giving the (WiFi) receiver system in the phone a better chance of being able to decode the data stream.

From what I've seen most consumer level WiFi routers are scanning with scanning is on by default so either you've landed on a rare one that doesn't or have accidentally turned scanning off (different manufacturers have different names for it).