802.11ax missing trigger frames

I took pcaps to verify some Wifi 6 features, and I think I am missing some frames.

Setup:

- 2 Cisco 9120's: one in flexconnect, one in sniffer mode

- Laptop that runs vWLC version 8.10.105 on Virtualbox, and serves as server for a speedtest.

- Laptop running Wireshark 3.2.1, receiving the frames from the WLC

- One client with Intel AX200 chip, one Samsung Galaxy S10

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vWLC and client confirm that 802.11ax is used. When performing a speedtest on the clients, the pcap shows a ton of consecutive RTS, CTS and 802.11 Block ACK frames, but no Trigger and/or data frames. I suppose that I should also be seeing these? Or are there any restrictions in what frames the sniffer sends to the WLC/Wireshark?

I would like to check stuff like which client gets which amount of RUs etc.

Thanks in advance!