SHEAR Failure of RAFT in STAAD PRO - need asap help

Hi, I am modelling a substructure in STAAD Pro and after application of loads when i ran analysis i got my raft failed in shear. my allowable shear is 0.675 KPa and the actual shear stress is 1.5 KPa, i have ignored the plates under the columns and even modified my mesh in such a way so that i can even ignore the plates at distance "d" from the face of columns but still the problem is there. my raft thickness is 450 mm . i have even increased the raft thickness to 500 mm but it also didn't work. i have created a group named as " RAFTSHEAR" to check the shear stress of Raft. my model is attached for reference. here is a link to my model

alfanargroup-my.sharepoint.com/.../EUTvNE-lGIBHmMg1_PC9pKwBpM8CIAV8D5vdTxbj7HydPw