This error is caused by a corrupt Translation Memory entry. There is something in the entry which is preventing it from successfully importing.
One example is from a Square Bullet Point brought in from a PowerPoint file. This can be seen in the example below before the words, "Example Text" and "HYPERLINK". It may appear as a symbol or unknown characters as seen below in 2 examples.
i="2"/> Example Text<bpt
i="3" type="987" x="89"/><bpt i="4" type="988"
x="90"/>HYPERLINK "https://sdl.com"<ept
i="4"/><ept i="3"/></seg>