What was the error? If a screenshot would be efficient, note that the Rescue environment has a screenshot capability. Just click the camera icon in the taskbar, and then a file save dialog box will pop up. A full screen screenshot will be stored wherever you choose to save it.
If the log of the job that created the F&F backup in question doesn't show any errors and the backup mounts properly in Windows, then I suspect this will be a quirk of the WinRE environment you're using and/or a transient issue. Again, a screenshot or at least a more detailed description of the error might be helpful. Since you're using WinRE, this may well be an issue new for WinRE 10 2004. WinRE causes your Rescue Media to be built using the WinRE files that match the kernel of the Windows version you're using. The problem that creates though is that if Microsoft ever releases a buggy WinRE version, then that can adversely affect Reflect. It's one of the reasons I stick to using WinPE 10 instead, since (currently) that causes Reflect to always build with WinPE 10 1709, a release that is not changing over time and that Macrium actually tested. WinRE had an issue with the 1809 release where the first version broke Reflect's automatic driver loading, for example. Microsoft recalled Windows 10 1809 entirely and the re-release didn't have that issue, but the early adopters who were using WinRE had Rescue Media problems simply because they updated Windows.
Lastly, as a general note, if you're using F&F backups and rely on browsing, be aware of the red-boxed note in this article
. Almost certainly not an issue if you're dealing with photos, but it's good to be aware of nonetheless.