Play or fight

I feel like I'm spamming this forum, but I never realized how much I didn't know. My chinchillas are both make, 8 month so, and have lived in the same cage since they were three months old (when they were both introduced to the pet shop. Yes I bought pet shop chinchillas. Save the lecture.). I got these two because they were cuddling at the pet store while they slept and they played together too. They seemed well bonded. Now they've lived together in a cage in my house for about a month. Suddenly, though, there's a lot of mounting and shoving and wrestling and they make this sound similar to a ducks quack. Neither are biting though and they go back to fairly normal right after every single time. Are they just playing, are they establishing dominance, or is this the first few signs of serious fighting? I have another cage, so I can separate them if absolutely nessecary, but it'd be less than ideal. I know chinchillas can decide not to get along anymore at any moment, but I heard those were typically fights that left blood and and scars and wounds. This is just light shoving and quacking noises.