In Errors window, long detail message may be partially hidden until clicked

In EagleFiler 1.9.3 (on macOS 10.14.6 (18G8022)), the detailed message at the bottom of the Errors window is partially hidden if it’s too long, with no visual indication that it continues.
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Clicking on the message reveals the rest.
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Sorry about that. This is a known issue that I’m planning to address. This particular error likely means that the e-mail file from Mail was overwritten by part of another file. You could Reveal the file in Finder and open it in a text editor to see what condition the data is in.

Great!

The messages (more appeared later) appeared blank in Mail; I didn’t think to try a text editor and didn’t see your post until I’d given up investigating. Fortunately they were just On My Mac copies, and capturing the originals directly from the IMAP mailbox went without a hitch.