Make sure that your tuplet definition is correct: 3, 8ths in the space of 2, 8ths. If you inadvertently set it to "use current" or some other numbers, that might explain the issue.

Here's a tutorial I wrote up.  

https://www.dropbox.com/scl/fi/4zei6hgq2lz0dh066re49/Tuplets-with-Simple-Entry.pdf?rlkey=5dwzi8o4b80om4r1mpvr7itox&dl=0

Yeah it's correct. I can reverse the rhythm and have an eighth and quarter with no issues. It's just that rhythm that glitches. 

Are you on a desktop or laptop? If this always worked in the past, but now it doesn't...

Step 1: Quit and restart Finale, and try it again

Step 2: Shut down the computer, wait a minute, and restart. Try the triplet again.

Make sure you are entering eighth-note triplets and not inadvertently asking for quarter-note triplets.

Not sure what you mean by "inadvertently asking for quarter-note triplets." I'm just using whatever the default speedy entry is. If I was able to enter the reverse of the rhythm correctly, I assume there's something else going on.  Also tried a restart and it's still happening. 

… Not sure what you mean by "inadvertently asking for quarter-note triplets." I'm just using whatever the default speedy entry is …

Unless you tell, what triplet duration you need (3 Quarters in the space of 2 Quarters, or 3 Eighths in the space of 2 Eighths, or …), Speedy Entry can only guess.

Speedy bases its triplet guess on the first entry duration after the keystroke Option-3.

If I understand you correctly, your entry string goes like this:

Option-3 ( I need a triplet …)

5 (… namely a triplet of 3 Quarters in the space of 2 Quarters …)

For your problem (= 3 Eighths in the space of 2 Eighths, but with Quarter + Eighth), try this entry string:

Option-1 (Opens the Tuplet Definition which defaults to 3 Eighths in the space of 2 Eighths …)

Return (… OK! …)

5 (… Quarter …)

4 (… Eighth …)

Gotcha. That worked! But I have to do those steps every time I want to enter that rhythm?

You should be able to use Peter's closing comment. Since the Option-1 defaults to the correct definition, you shouldn't need to do any more than those two keystrokes before entering your pitches. (I tried it, but I couldn't make it happen, due to my unfamiliarity with Speedy. Simple is just as easy, but with different keystrokes.)

I've been doing this for years-

With either Speedy or Simple enter in 4/4 time - 1/4 note then the 1/8 note (no ctrl-3), in 2/2 time - 1/2 note then 1/4 note

If complaint about too many beats in the measure comes up, Leave measure alone

Select the Triplet Tool click on the 1/4 note or 1/2 note if 2/2 time

Select in 4/4 time [3] Eighth(s), in 2/2 time [3] Quarters

Select in 4/4 time [1] Quarters(s), in 2/2 time [1] Half(s)

OK

Works every time.