Error using 'On Trigger' mode

I'm trying to force one parallel chain of nodes to execute before another by using the 'On Trigger' mode to initiate the second chain after finishing the first one. All I'm doing is connecting 'OnExecuted' of the last node in the first chain to 'OnTrigger' of the first node in the second chain. At first, all goes well and the chains start executing in the desired order, but when it gets to the node with 'OnTrigger' it throws this:

```
!!! Exception during processing !!!
Traceback (most recent call last):
File "C:\AI\ComfyUI_windows_portable\ComfyUI\execution.py", line 135, in recursive_execute
input_data_all = get_input_data(inputs, class_def, unique_id, outputs, prompt, extra_data)
File "C:\AI\ComfyUI_windows_portable\ComfyUI\execution.py", line 26, in get_input_data
obj = outputs[input_unique_id][output_index]
IndexError: list index out of range
```

My actual workflow is way too complicated for this, but this here has the same problem: