We have a small three of three, including me as a PM/BA for the project. Every month we have a release, and the two developers which I have have different levels of experience. The senior fellow has been a committed individual till now, and the junior colleague is a hard working girl who is improving her expertise as we go along.
In the past two releases we have had slippages, but to no account of their hard work, mainly in terms of Infra issues and resource availibility issues (no redundancy!). However, this release I have tried to address all these issues beforehand, but the Senior developer has gone rogue, he hardly replies to my emails (am not in same geographical location), does not pick up his phone most of the time. He had a planned leave, and I already have people for the handover to continue the development work, before leaving he was responsible for sharing estimates for the next set of requirements, this task complained to be a , so this time we tried to reduce his work by half. Yet, he did not deliver till Friday evening (we submit these by Thursday usually), and again did not inform me through email or phone (inspite of earlier confirmation that he'd call me and share the estimates). Apart from this, the same behaviour has applied to other project actions/responses.
Am deeply concerned with his behaviour, part of which I can attribute to other aspirations which the project cannot fulfill. He has discussed these in the past, and I have told him that if he finds something better I will not stop him (he deserves it too). Am contemplating raising it with his supervisor formally now. Last week I had a discussion with his supervisor who stated that the developer assured no slips in delivery. This is something which I absolutely wish to avoid, I have never done this before, but I already see us delayed in work due to this. I also know that once I drop that line, his plans for any better aspirations would be stalled too. What is the right thing to do here?