@dchow @CoskuTurhan “`Hello Jake, There are two phases to cooking a DOP frame: the network pass and the solve pass. Former takes care of setting parameters and building the sequence of operators that are to act on the objects; the solve pass then actually invokes these operators. The issue is that substepping triggered by the Gas Substep solver is done as part of the solve pass, while the Switch Solver gets its switch value set during the network pass. To perform its solve, Gas Substep DOP basically determines how many substeps to take and calls its sequence of input operators that number of times. So when the Switch Solver is reached, it uses the switch value that was evaluated at the network pass. In other words, the value of that parameter does not get refreshed for each of your substeps.
You can get the behaviour you want by disabling Override with Default and using the data specified in Switch Value Name. This data will have to be modified to account for your frame number logic, which can be done fairly easily with a Script Solver. Note that this works because the parameter value is static (name of the data to use), but the actual data stored gets evaluated every time the node goes to perform its solve. “`