Roon
Interface & Usability
Cross Contamination of Last.fm Scrobbles
Linux (NAS/SonicTransporter/Antipodes/Ubuntu/etc.)
Custom build with Ryzen CPU
Auralic Aries, Elac Discovery Z3
Ethernet
I have multiple profiles on my Roon setup, two of them have unique Last.fm profiles configured. I am getting cross contamination, I am seeing the other users playback scrobbled in my last.fm account. I am confident (reviewed play history in Roon) that the correct profile is configured and selected. Using 1354 on the server and 1348 on iOS devices for remote.
I have confirmed that this is definitely happening as described, I now have a significant list of cross contamination in my last.fm account - this isn’t/wasn’t a one-off anomaly.
Does it happen only if you interact with their music (like pause what they played)?
Based on a recent ARC bug relating to Last.Fm, that the recent builds were meant to fix, I am wondering if all the issues the latest build introduced are caused by constant updating of Last.Fm.
I don’t interact with their music playback at all, in fact it has entries where I was traveling for a few days and my only use was using Arc; yet my last.fm history shows the music that the other person was playing in my house.
I verified by looking at the playback history in Roon that they were using the correct profile. It’s really obvious to me that the scrobbles are from the other user, it’s not even a genre of music that interests me.
Bumping as I just checked and my scrobbles are still being contaminated with another users playback history.
I haven’t checked mine (can if you want me to), but just adding weight to this, as a user of lastfm, this would really suck. 
And we should fix it.
Yep, it really does suck.
Looking back through the “My stuff” history in Roon and the Scrobbles for each account it is apparent that the contamination is only one way. While my lastfm scrobbles are being contaminated by their playback the reverse is not true. Their scrobbles do not include my music. What I have noticed is that it appears that their activity is duplicated across the two lastfm accounts.
Suck isn’t the word here, now I have come to the realization that my last fm data is absolutely trashed. It’s too late to fix anything now, there is months of someone else’s playback history impacting my stats there and now the inaccuracy of that data makes last fm worthless to me. I think that I will have to just trash my account and start over once this has been fixed, that is nearly four years of data gone.