pre action protocol - defendant responds advising may be out of time

[GISMO1989]

If a defendant responds to a pre action protocol accusing the claimant they are out of time, how can the claimant move forward? Do they apply to court to have the time barred accusation striked out?
Does equality act 2010 cover a claimant for not binging a case to court sooner due to mental health?

[GISMO1989]

Further:

Pre action protocol sent by claimant.
defendant responds two weeks later advising they are looking into the claim and will respond ASAP. Defendant makes note claim may be out of time.

bullied and harassed in the MOD 2008-2010. Bullies reported by several people including claimant , but mod done nothing.
claimant is unwell, signed off work by mod for months and treated for depression. Claimant requests early release from mod while receiving treatment, mod accepts, claimant leaves in 2010.
Mod doesn’t put claimant to medical board despite claimant being suicidal, mod just signs claimant off work and makes note in medical records that soldier X will be fit when they leave the mod. This of course wasn’t the case.
Frequent doctors visits, mental health treatments and therapy sessions between 2011- present. 2016 private psychiatrist diagnosis claimant with PTSD. claimant still receives treatment to date.

Can the reason for the claimant not bringing a civil case to court sooner be argued that they were unwell under equality act 2010or section 33 in limitation act?

How does claimant argue with defendant that the case is not out of time? Does the claimant need proof from court first? Or can this be argued in ore action protocol mediation?