Unable to get proper modulated wave in GMSK modulator

I have designed a GMSK modulator. Input 1 is Bernoulli binary, 2 and 3 are sin and cos respectively. I have passed the binary signal to a unipolar to bipolar convertor, then filtered using a Gaussian filter, added a Gain block to down-sample before integrator block, and then added a gain of 2*pi, passed it to sin and cosine lookups and then did the product with sin and cos, then used add subtract block. Then to check if the block is getting modulated or not, I connected the modulator block to an ideal GMSK demodulator block from simulink. Since it takes only complex input, I used a real-img convertor. But I'm getting the error rate as 0.4, which shows the data is not receiving correctly. I have been debugging this, but unable to understand where exactly is the issue. It would be great if I could get some insights. I have also correlated the scope output of the designed GMSK modulator with that of an ideal GMSK modulator, I'm also attaching the screenshot for reference.

[Vasant]

I think the product with sin and cos is resulting in the disrupted wave, but don't know how to make changes.

[Souparnika]

But that product is required to get the modulated wave right? How to do it in other way?

[Vasant]

Does the gaussian filtering resulting in the issue?

[Souparnika]

I calculated the filter coefficients using 'gaussdesign' function within matlab, and then took the coefficients and then added it in the coefficient parameters of a 'discrete FIR filter' block within simulink.