[Closed] Rockshox Monarch Losing Air After Service

I've recently self-serviced the air can on my Rockshox Monarch. On the last ride the shock lost air after a biggish (for me) hit. I guess this must be because the seals failed at high pressure. The seals were replaced in the service so it must be because they've lost lubrication. When I took the shock apart there was some residual mucky oil in the air chamber but the Rockshox service manual didn't say anything about adding oil so I didn't.

Do people recommend adding oil or soaking the foam ring in oil, and if so what type/weight? (I have 7.5 and 10 suspension oil plus engine oil)