How do you know that the recent failures are not just coincidental? I think its impossible to know! These could be just random failures. I'm sure ISRO is doing the best job they can. When there are failures, ISRO will learn from them so that the chance of them happening again is greatly reduced.
Just looked at the mission brochure; the second stage will not use the HTVE-Vac engine (846.8 kilonewtons), but rather the Vikas 2B engine (803.78 kilonewtons).
The 32 hr countdown activity has commenced at 20:04hr IST on Tuesday, April 10, 2018 for the launch of PSLV-C41/IRNSS-1I Mission scheduled at 04:04 hr IST on April 12, 2018
On addition of any new safety mechanism in IRNSS-1I to avoid power failure, the chairman said, “Power systems used in GSAT-6A and IRNSS-1I are totally different. The power system being used in IRNSS-1I is very simple and proven as all seven navigation satellites launched earlier are working successfully.”