I recently outsourced a libre office document and when it was returned the formulas that had been inserted were all in strange images despite the correct formula being clearly entered. Also, the incorrect symbols actually appear in the elements block, for example, there is a picture of an envelope instead of a plus (+) symbol and when I hover over it libre office still tells me that it is a plus symbol. I went into fonts on the menu and found that all text/objects had been set to times new Roman and not anything peculiar so I do not know what to do.
@Petestf90 - I interpret the your word “outsourced” as you gave to file to someone else and you don’t know what was done with file until you received it again. This is supported by the fact that you do not provide any information on what happened with file before it got “strange”. Please understand that under this conditions it might be/is impossible to provide you an solution.