First, thanks for responding to my initial problem report.
So, per your recommendations, I've uninstalled Tera Term Pro 2.3 - and installed Tera Term 4.91.
I'm running Tera Term 4.91 in a Windows Server 2008 R2 x64 system.
I would have to say that 4.91 is actually a bit worse than 2.3 in regards to my problem.
I'm still occasionally getting weirdly rendered text - but with 4.91 the oddly rendered text isn't even remotely "texty" looking.
It looks more like some odd combination of line / block drawing glyphs. It's not almost human readable like it was when using TT 2.3.
Here are some screen snapshots showing what appears in the Tera Term 4.91 VT100 window vs. what gets displayed when I copy 'n paste the oddly rendered text into a Notepad session ...
At this point, I should add a little something to the explanation of how TT gets itself into this mode.
I'm issuing a command to the device under test - that requests the device to do a warm reboot of itself.
On every reboot, the device starts spewing out "random stuff" on its serial port for a short amount of time, then it eventually settles down and sends "proper data" at the expected Baud rate, Parity, etc. I'd estimate that 75% of the time, this reboot operation is uneventful and Tera Term doesn't get all confused about what characters to display.
But 25% of the time, Tera Term ends up displaying weird characters.
And the weird characters are only associated with incoming data that are standard ASCII lower-case a-z.
I'm guessing that the initial "random stuff" sometimes includes some odd sequence of bits that Tera Term happens to recognize as some (obscure?) escape / control sequence that puts it into "weirdo mode".
I guess I'm looking for advice on how to configure Tera Term to either ignore this particular escape/control sequence - or if it can't ignore it, at least configure it to choose an appropriate alternative character map such that it still displays human readable text.
I've included the TERATERM.ini file - though I have not made any changes from Default (yet).
Thanks in advance for any words of wisdom.