Combiner Functions Seemingly Not emitting correct results

So I'm working on a test streaming case. Reading from pubsub and for now, sending to stdout for some visuals on the pipeline and transforms.

I believe I'm getting some unusual output, and believe I'm likely missing something so hoping someone can help.

Take my code (stripped back to debug):

with beam.Pipeline(options=opts)as p:
    (
    p
        | ReadFromPubSub(topic=topic_name
                        ,timestamp_attribute='timestamp')
        | beam.WindowInto(beam.window.FixedWindows(beam.window.Duration(5)),
                         trigger=beam.trigger.AfterWatermark(),
                         accumulation_mode=beam.trigger.AccumulationMode.ACCUMULATING)
        | beam.CombineGlobally(beam.combiners.CountCombineFn()).without_defaults()
        | beam.Map(print)
    )

I am generating an arbitrary number of events and pushing those to my topic - currently 40. I can confirm through the generation of the events that they all succeed in reaching the topic. Upon simply printing the results of the topic (using beam), I can see what I would expect.

However, what I wanted to try was some basic window aggregation and using both beam.CombineGlobally(beam.combiners.CountCombineFn()) and beam.combiners.Count.Globally(), I notice 2 things happening (not strictly at the same time).

The first issue:

• When I print additional window start/ end timestamps, I am getting more than 1 instance of the same window returned. My expectation on a local runner, would be that there is a single fixed window collecting the number of events and emitting a result.
• This is the DoFn I've used to get a picture of the windowing data.

class ShowWindowing(beam.DoFn):
    def process(self, elem, window = beam.DoFn.WindowParam):
        yield f'I am an element: {elem}\nstart window time:{window.start.to_utc_datetime()} and the end window time: {window.end.to_utc_datetime()}'

• And to reiterate, the issue is that I am not getting 'duplicate' results, it is rather I am getting multiple semi-grouped results.

The second issue I have (which I feel is related to the above but I've seen this occur without the semi-grouping of elements):

• When I execute my pipeline through the CLI (I use notebooks a lot), and generate events to my topic, I am getting considerably less output back which appear to be just partial results.
• Example: I produce 40 events - each event has a lag of half a second. My window is set to 5 seconds, I expect (give or take) a combined result of 10 each 5 seconds over 20 seconds. What I get is a completely partial result. This could be a count of 1 over a window or a count of 8.

I've read and re-read the docs (admittedly skipping over some of it just to seek an answer) but I've referenced the katas and the Google Dataflow quest to look for examples/ alternatives and I cannot identify where I'm going wrong.

Thanks