Value disapearing when using YTD measure on Matrix visualization

It's not clear if the measure in these 2 matrix is the same. I will assume so. The existence, or not, of a second measure in a matrix cannot affect the first measure, so that is not the cause. It seems the columns in rows in both matrixes are different. This is the likely cause. I suggest you create a new blank page, add 2 matrixes containing the measure in question, then build both matrixes. Watch carefully to see what works and what causes it not to work. Then investigate what stops it working.