How to reliably share files and folders between Windows 10 PCs

I have followed various different tutorials on how to setup file sharing over the small LAN I have. There are two PCs and One Laptop which all run Windows 10 Version 21H2 Build 19044,1826. I also have two VMs running Windows 10 21H2, two VMs running Windows 11 and three VMs running Ubuntu (various releases but not involved in this problem).

When started the two main PCs , both of which have the FDPHost, FDResPub , SSDP Discovery and UPnP Device Host Startup Type set to Automatic correctly show up in the Network section of File Explorer. They all show the folders that have been set as shared and can be modified and opened and closed as the permissions of all of them have Everyone as Full Control. When the laptop is started it sometimes acts in the same way but with a problem. The folders do not always allow access.

I have discovered that Restarting the FDResPub service can cure this sometimes, but not always. On some occasions the remote laptop will show the folders but deny access to them. If i try to access the laptop from the file explorer of one of the main PCs by typing the machine name or the local IP address the laptop will appear and sometimes demand to have network credentials entered.
I do not know what network credentials are.
Some of the time the laptop is started by a user with a different sign on; could this be the network credentials that it sometimes requests?

Is there something else that needs to be checked?

It would seem that someone with detailed technical knowledge of how Function Discovery works would know the ins and outs of this problem.

I have avoided tackling the Windows 11 situation which is what I am preparing for but has shown some symptoms of the same problem.

Either a NAS or use a Cloud service, which is the way that computing is heading.

Depending on the amount of files you want to share and your router, many/most routers these days now have a USB port that can be used with portable hard drives and/or USB sticks to provide an easy alternative to sneakernet.

It's an easy alternative to navigating the joys of network discovery/authentication, etc., particularly when you have a mix of different OS platforms in use.

Hope this helps...

@Samuria, Thanks for the info. I will have to try that on the laptop to check if it works.
@bro67, Thanks for the suggestion but I do not want to spread the files outside my control.
@RickC, Thanks for the suggestions but swapping USB sticks or other things is too slow. I use the second machines for working on projects and the first machine to download from the internet and have extensive security to check for rogue and/or malware before copying the parts required to the working machine/s.

MacNala said:

@RickC, Thanks for the suggestions but swapping USB sticks or other things is too slow.

You don't swap them. You leave them permanently attached to your router as a very cheap form of network-attached storage rather than buyng a dedicated NAS.

@dalchina, Thanks for the extensive considerations. Your comment about SMB1 has more to it than "is it enabled or not". Please expand your reason for the comment.
I have tried all the methods in the article/tutorial you quote and found them wanting at times i.e. they don't always work.
I have found that FDResPub if restarted seems to solve most (but not all) of the problems of reliability. I intend to use PowerShell Remote sessions to the other machines to help automate the propagating of the data and code I need for the project/s and for this Networking and Sharing must be Reliable. I have read some of the items about failing to share Win11 files with Win10 machines and am starting to wonder if it is a marketing ploy by MS to promote the cloud. The demise of File History is one of those steps.