Without something like that, it feels like we're being strung along. I'll repeat a previous suggestion: Have a leader from the engineering team communicate with us directly herein as to status, progress and mitigation time frame. For sure we should have heard more by now. In the world of mission-critical enterprise software development, this kind of pace and execution would typically be intolerable. Lacking is any sense of time frame for mitigating the problem. We're simply told that the engineers are aware of the problem and looking into it (I'm paraphrasing here). The problem is also how slowly it is taking for Dropbox to identify the root cause(s) of the problem and being transparent by letting the Community know, at minimum, why the problem is happening i.e., via update reports as to status and progress.
Problem is not just the thumbnail viewing per se (lack of for local image files).