Variable size to Fixed step discrete - sample time?

Hi,

I have a Simulink block with S-function Level-2 which was working fine to control switching on and off of devices. It was run many times successfully using variable step ode23tb.

For collaboration purpose, I need to integrate a new block into the above system. This new block is designed in fixed-step variable with a fixed sample time at 0.1s (discrete no continuous state). Ever since I integrate this new system to my current system, the simulation results got wrong.

I suspect it is due to the solver option or sample time, which I am really new to these.

What I have done:

1. Once I integrated the above two systems to the same Simulink file, I changed the configuration parameter to Fixed-step, discrete no continuous state

2. There are two places I need to define sample time: one is at zero order block and another is at the new system, so for both I set to the same value, 0.1s

I was wondering:

1. Is it possible to integrate two system above? If it is possible, what are the necessary modifications? 2. Could it be the synchronization problems/ If so, which aspect should I look into?

I just need to at least have a direction on what to troubleshoot, I appreciate any reply, please, thanks