When you get strange characters (possibly from one of the WingDings or WebDings variants), look at the chosen font for the field. How it gets that way? Don't know.
As a side note, check how many DIFFERENT fonts you use in the same report. Should not be more than two or three. (Not talking font SIZES.) Arial, Courier New, Times New Roman.... that would do it.
You should know this about Access (and other MS variants). KeLsO is right that you should avoid use of "oddball" fonts. They might end up substituted for something else.
BUT... if you happen to remove and re-install a font, you break the link to it sometimes. When that happens, it is a "True Type Font" standard response to try to find the nearest matching font based on characteristics stored in the font header. However, what constitutes "nearest match" is anyone's guess most of the time. And that is how you sometimes get the wrong font selected.
It doesn't matter if you didn't remove a font. If you UPDATED a font, it could have removed an old copy with a newer one. And many MS (and other) packages will install new fonts that might overlap existing ones. I know Word Perfect will do this now and then. Some third-party font collections do it all the time. So a random install could have done it to you.