Hi all,
I am still not sure this is the only root for the issue I am experiencing but with the great help from this forum it seems that I am getting “Network Error” message on Server v3 during the smart scan and even stage mapping sometimes is because my SD cards are crap (they didn’t cost like crap but that didn’t help). Do you have recommendations for what SD card to buy? Or is there any other way to get to solve this issue?
Thank you 
First, a post covering the SD card part of your question:
Are your SD cards specified/marked with an ‘application class’ rating, as in marked A1 or A2?
Most SD cards are aimed at use for cameras, storing photos or videos, which are large files that are rewritten a relatively small number of times. An operating system on the Pi, or an application on a phone, makes many many small reads and writes to small files. This requires different optimisation for ‘speed’, and I think also for lifetime.
We have very recently done some more investigations of the actual speeds available on the Pi, and the meanings of the various specifications for SD cards. We have updated the part page for the SD card, and added an information page. This was after the current v7.0.0-beta5 release, so it is currently in the development version at Assembly Instructions . This will be in the next release.
The lowest cost cards that I can get with appropriate ratings are actually the branded Raspberry Pi cards. I think this is because most of the manufacturers see A1, and particularly A2 as high end cards and combine them with read/write speeds of 100MB/s and above. This is great in places where you can use it, but the Pi side of the SD card interface has a maximum speed of ~50MB/s so it is not useful in our case.
I have not yet actually tested any of the batch of new cards that I got after we reviewed this specification, and anyway I am mostly changing hardware, so my cards don’t get worked hard at all.
Second, is it actually the SD card?
From your other posts, you are mostly working on the v3.0.0-alpha software. There could possibly be problems with that. In the past, if you had a Windows PC you would find that it needed to be shut down and re-started regularly, and you probably had to re-install from scratch after a while. It seemed that things in the background were not closing cleanly, leaving loose ends of processes or loose items in configuration and temporary files that caused other problems. I don’t think that this is a problem for Linux in general, or the underlying Pi OS that we use. I think the way that you tell the difference between SD card problems and OS problems is wheter re-flashing the operating system to the same card gives the same life before it plays up again, or wheter the operational life is getting shorter each time, and is lengthened again if you use a brand-new card.
If a new SD card is the only way to solve the problem, there are different things that can cause a card to fail early. One is the design of the card, as in my first post. The other is how the card is treated. SD cards certainly like the Pi to be powered down cleanly, using shutdown in the software, rather than just cutting the power. It might be that power fluctuations, particularly voltage drops, also give reading or writing errors or physically damage parts of the memory on a card. A Pi runs towards the upper limit of the USB 5V power specifications. Any problems in the power supply, cable, or connector could cause low voltage. The Pi can report that to the desktop, but really you would want a log to see the levels and how often it happens (and we don’t yet have a version of the v3 software with desktop.) With my phones, the charging connection varies a lot with supply, cable and how dirty the connector is. At least the microscope USB socket does not need to cope with being in pockets and sports bags.
Thank you so much @WilliamW ! Reinstalling from scratch did help for a bit but the lifetime was getting shorter and shorter. I think I also wasn’t treating them well to be honest, it was hard for me to tell whether the rPi has switched off properly so I am sure I plugged the power cord out two early on more than one occasion. I will look deeper into best practices for that. I have ordered a couple rPi SD cards, let’s hope they hold for longer