Vodafone ADSL - after uploading a file, we're unable to download anything for up to 15 minutes

I've had an ongoing problem for months and months with our Vodafone broadband connection

Every time we upload a file (ie: when I take a photo and my phone uploads it to google photos, or if my wife is uploading photos to a greeting card making website) , after the file is uploaded our internet connection stops working for 5 to 15 minutes

We're on an ASDL connection, which is the fastest line available at our location (we live at the edge of a small town)

I had a support ticket about this 4 or 5 months ago, they performed a 24 hour monitoring test and told me...

Upon investigation we could find no fault over the network. There is no data loss or delay that we could find as well

I've noticed that your upload speed has been maxed out. Once there's a high usage of the upload speed, it will affect the stability of your download speed, that will result to disconnections

For the meantime, you can try to do a factory reset on the modem by pressing the reset button/tiny hole at the back for 30 mins (you can use a pin) to refresh the modem, and moving forward, kindly balance the usage of your upload speed as sometimes it would take time for the connection to be back on track.

So their advice is to "balance the usage of your upload speed", but I have no idea how I can do this. We aren't doing anything out of the ordinary with our uploading, it's really mainly google photos and sending photos and videos via whatsapp etc

Does anyone else's internet connection work like this? If there's nothing that Vodafone can do, I'm going to have to switch to another provider. Our internet cutting our every time we upload a file is massively annoying