Migration Assistant: some files could not be transferred

I have a 2017 MacBook Pro (13” (two Thunderbolt 3 ports) running macOS Catalina 10.15.7) that I recently got back from the apple store after some repairs. I had been using a temporary 2015 MacBook Pro (13”, early 2015, running Catalina 10.15.7) while the other one was getting repaired, and now I would like to transfer everything over from the 2015 to the 2017. However, I’ve run into various issues. I have tried the following:

1. I backed up the 2015 Pro to an external hard drive using time machine. I connected the hard drive to the 2017 Pro and then used Migration Assistant to try moving everything over (note: the 2017 MacBook Pro has NOT been factory reset). After about an hour of starting this process, it told me that there were ~20 hours left, so I let it run overnight. But the next morning, it was still stuck at ~20 hours left. So I aborted this attempt.
2. I decided to try something different. Instead of using the external hard drive, I instead tried migrating directly from the 2015 Mac to the 2017 Mac over WiFi. This seemed to be working. A few hours later, it seemed to almost be done, but then gave me the following message:

Sorry. An error occurred while transferring your information.

Some files could not be transferred.

Some documents for <insert my user account> could not be transferred.

      1: <insert document name>.

Some files from <insert a directory name> could not be transferred

Some files from <insert another directory> could not be transferred

I wasn’t sure what to do, so I just hit continue. The next screen said “Migration Complete” “Your data has been migrated and is ready to use.” So I hit quit (which was the only option).

Now, I wasn’t confident this had worked, so I started to compare the sizes of various directories between the 2015 and 2017 Macs and there are many differences. These were all directories that were in my User account, but I don’t think they are related to the error message I got above.

I am really not sure what to do. Please help!!