Problems with Arial "s" and "t" characters

[Rodrick-EPL]

Hello, comrades. I have a problem related to fonts in Indesign that I've never seen anything like it and I have no idea how to search to solve it.
Specifically in the "Arial Regular" font, when the characters "s" and "t" are side by side, a curved line appears from the upper point of the "s" to the top of the letter "t". Always in lower case.
If anyone has experienced this and/or knows how to solve it I would be very grateful.

Attached is a photo and file with the problem.

Live long and prosper! 🖖

[BobLevine · Accepted solution]

Turn off the ligature if you don't like it.

[Steve Werner]

I opened up your InDesign file.

When I select the words affected I don't see the "st" issue which looks like a ligature.

But when I look at your paragraph style, it looks like you have Contextual Alternates turned on. Try turning it off.

I suspect that that's the issue.

[Peter Spier]

It's not, apparently, a contextual alternate. I tried turning that off before posting.

[Rodrick-EPL]

It worked.
I hadn't seen this before because we changed fonts recently.
Thank you very much for the objective and quick response.

[Peter Spier]

That's a ligature. and the s-t ligature is not particularly common, so I'm surprised it's included in Arial.

You can turn off ligatures as part of the style assigned to the text or as a local override. Turning off ligatures does not seem to affect the f-f ligature in Arial.