We've also been getting this constantly for years now and it's really driving me crazy.
Perhaps we have a different issue with our database or my methodology is bad, but when I assign a job to myself, I hit apply to save the change and allocate the job to me so another admin doesn't pick it up. I then leave the window open and fix the issue for the user, and then update the solution field, and every time without fail it gets the "You cannot update this Service Request because someone else has already updated it" message. I've learned as others have to just use notepad to type your text, and then paste it into the field, but this gets more than a little annoying every single time you respond to a job.
What is the correct workflow to stop this happening? Do you guys normally open the ticket, assign it to yourself, and then shut down the browser and open it again whenever you need to update a field? I'm used to always "applying" any fields I update or modify with other applications, but it seams in Sysaid, this can only be used once in a session, is that right?