There seems to be a bug in the UDT parameter stuff right now that causes them to resolve as float/doubles, which in the case of these Modbus tags is turning the address from something that would be for a register, e.g. [Device]HR1 into something for a bit write, e.g. [Device]HR1.0.
This was supposed to be fixed in the 8.0.11 release but there’s apparently some case or cases that are still broken.
I think it’s the same thing as is happening in this post: [BUG]8.0.11-rc1 Numeric UDT parameters now appear as floats when used in OPC_Item_Path