I have been working on a specific project for going on 4 years. I have recently begun having an issue where the fonts of the traffic signs are displaying improperly. Where the project-wide fonts are mostly Clearview and Highway fonts, now no matter what file I open up, the majority of the Clearview and Highway fonts have been changed to fonts such as Standard, Verdana, and Univers57 Condensed Oblique. Strangely, some of the Clearview fonts were retained here and there. The sign fonts have been displaying correctly for years, and then one day they didn't. I am able to manually change the signs fonts back to their original fonts, but as there are thousands of signs this is not practical. Other fonts on the sheets seem to be unaffected, just the fonts in the signs themselves.
Can anyone offer any insight as to what the problem might be? Thanks in advance.