What is the biggest issue with engaging an expert witness?

To all the people in my network who engage Experts for Expert Witness Reports (in any field).. What is your biggest problem or dissatisfaction with these reports?

Are they too technical and hard too decipher?

Is the formatting and numbering poorly executed?

Does the 'Bates Numbering' on the different documentations provided not line up across the board?

Deadlines not being met?

Reports are biased and not independent or leaning towards the client's preferred outcome?

Keen to hear some thoughts...