Certain characters within an attribute value (in your case the onmouseover attribute) must be encoded, as they have a reserved status in HTML. In this case, the < and > characters denote the start and end characters of a tag, eg:

The last time (and the years before) I worked at that code

Which version was this?

I dont' think JCE has ever allowed code like that within attribute values without encoding it first.

Please post a link to an article containg this code.

I've checked you code with various versions of JCE Pro going back to JCE Pro 2.8.18 and in every instance the <> characters are encoding in the attribute values, as they should be.

The code you are using is technically invalid, as <> symbols must always be encoded in attribute values (along with some other symbols), and JCE will always do this to create valid code.

Perhaps you added and saved your code with the editor off, or in the Code tab? Going forward, to maintain the code as it is, you will need to ensure that you edit that article with the editor off, or using the No Editor option in the Joomla Global Configuration.