Is the link obstructed at all?
If not, then it looks like you are aligned on a side lobe of your signal, I would recommend taking another look at your alignment. With how close your antennas are and how much power you are using you really should be minimally in the -40s and the Mimosa tools say you should be in the -30s.
For best alignment at short distances, I would recommend dropping your TX power on each side to something really low, that way your side lobes will be really difficult to align on and only the main lobe will give you a good signal to work off of. Once you have the link aligned increase TX power to EIRP limits and you should have a pretty good link for what you are doing.