There's a number of things that can be improved on in your flow that will help prevent issues down the road. First of all, set the values you're passing directly into your inject node.
Have one for your coil read and one for your register read. You don't need the functions to set the information for the MODBUS query. Also, add a topic or something as an identifier. You'll want this later.
Second, tie both of your inject nodes into ONE flex-getter node. This is how they were intended to be used. This is how you keep the traffic collisions out.
Next, tie the output of that into a steering function and steer your messages accordingly.
So in the end, you have a setup more like this:
There are several ways to optimize the flow further, but this will get you the setup you want without having any collisions and downtime. This is how you'll want to setup your MODBUS routines to make sure they work smoothly and without the flow causing issues. Give that a shot and let me know if you have any issues afterwards.
EDIT: You'll likely notice in that last image I have several unknown nodes. I don't have those nodes installed so it won't list them. That's also why I can't post the flow as it sits, because I don't have those nodes installed.
