I saw this #AskAgent question on Twitter recently. Since I don't answer questions on Twitter (no room for nuance and no way to filter out the frenzied), I'll post it here:
When querying, does it scare agents away if we mention we've worked with agents before? If we've had two agents abandon us mid-project (different projects) does that make us look more legitimate or suspicious? Asking for a friend.
The query you send me should be about the book you want me to take on.
And about you.
Your past (horrifying) experience with agents is best left till later. Much later.
The sad truth is, my first thought is: this writer is trouble.
If two agents ditched them abruptly, that's a red flag.
Don't fly your red flags if you can help it.