When I replace English words with Spanish ones that have accents I always get this error and my text block has a red box

Translation is not valid: <span style="color: rgb(102, 102, 102);line-height: 18.7px">&amp;nbsp;</span>&amp;nbsp;<span style="color: rgb(102, 102, 102);line-height: 18.7px">....  followed by my Spanish text.
However if I paste a French text with French accents I don't get this pb. Is there a work around ? English and French seem to work together.