I agree with DaveB (mostly) According to Strata Community Australia’s “Who’s responsible for what …” document, tiles fixed to common walls or walls adjoining common property are the OC’s responsibility. I too think a splashback should be treated as if it were tiles.
However, when you refer to “our strata insurnace” do you mean your own home contents insurance or the Owners Corporation insurance?
Also, FYI, the Who’s responsible memo is not law and it may not even be part of your by-laws but it is referred to by strata managers, Fair Trading mediators and CTTT adjudicators when considering cases.
Summing up, if the splashback is on an internal wall, it’s your problem. If it’s fixed to an external wall or a wall adjoining another unit, you have case to say it’s the OC’s pigeon.