When creating List items in SharePoint online through the NewForm.aspx URL, attachments are not being included in generated items roughly half the time. Items are generated with all other information, but no attachments when the bug occurs. This only occurs when using Modern Experience, not the Classic Experience.
Behaviour is unrelated to attachment size, name or type, and has been tested across multiple tenants and sites. Various browsers were also used, and Microsoft Support also recognised the behaviour but could only recommend making an Idea. Which I have, but would also like to check in with the community.
Anyone else affected by this problem (albeit quite a specific bug)?