Background: I was an involuntary landlord for a year due to job loss/injury so I used a letting agent to manage things (I know I'm still the responsible person). The tenants moved out early August (over 90 days ago). They caused much damage, amounting to almost £4000. I did everything I could to keep the costs down, doing much work myself and only asking for the materials etc. I only got labourers in when it was beyond my expertise. The agent has agreed that it's damage beyond wear & tear (which I understand for a 12-month lease, should be minimal).

However, it is not surprising that they are contesting me, even though I have evidence, as they want to retain their deposit, which is less than half of my costs. But despite being advised to raise a dispute by the agent, the tenants have not done so and I'm at a loss as to what to do, and how to get this resolved. When the tenants were delaying/time-wasting previously I sent a letter before action for the full amount, which they have confirmed receipt of and this was the point the tenants said they'd raise the dispute but it's all words no action.

The agent seems to have their rule book/process to follow, which is totally fair, but I'd really appreciate some more nuanced information about how long we have to give them to raise the dispute. In my viewpoint, we're stuck in a deadlock and dependent on the tenants to act. Does anyone have any insight from the landlord side/or questions I should be asking of my agent, please?

EDIT: Clarity