Costas Loop oscillates in ModelSim while locks in MATLAB!

--- Quote Start ---

Is the filter in floating point in matlab? Or fixed point?

The VHDL will be fixed point - are there any rounding errors or parts where the bit width isnt wide enough?

--- Quote End ---

I tried to use multiples of 2 as far as possible in matlab. This is the block diagram of the loop filter where C1 = 4 and C2 = 1/2^8

https://www.alteraforum.com/forum/attachment.php?attachmentid=10459

In VHDL, I tried every thing regarding rounding errors and bit widths... this is the best result I got or the closest result to matlab results. I widened vectors in almost every where in loop filter.