@Tony Johansson Welcome to Microsoft Q&A Forum, Thank you for posting your query here!
I understand that you are expecting a most reliable solution to trigger the Azure Function upon Blob Upload / write via BlobTrigger.
Please note that our documentation clearly mentions that if you are executing your function code based on changes to blobs in a storage container, and the Blob storage trigger might not be the best option.
See here.
If you require a faster or more reliable blob processing, consider creating a queue message when the blob is uploaded. Then use a queue trigger instead of Blob Trigger to process the blob.
Another option is to use the ***EventGrid .
This*** article explains the detailed action plan with various strategies that can be followed to achieve a faster and reliable blob processing. Hope this helps.
Please do not forget to "Accept the answer” and “up-vote” wherever the information provided helps you.