I believe that it may well have been bird strike or other engine fault that made him fly lower than the rest of the Arrows, but I believe quite firmly that the problem that actually caused his death was down to an ejector seat problem. ?
He was seen by those that were quite close to the impact area to be fighting with something down between his legs, as he was head down and clearly struggling with something. Those guys would never have dropped the gear when they were about to make a forced landing on a soft surface, but his gear was dropped ! Remember that a few weeks later another Arrow pilot was killed by some fault with his seat.
All aircraft fitted with that type of seat were subsequently grounded temporarily which tells us that there was indeed a problem with that ejector seat design. Quite why Red 4 dropped his gear and then fought with something, maybe a locking pin in the seat underneath him, is unknown, but most unusual as if he was stuck in the aircraft, he would certainly have attempted a belly landing on the fields that were around him ?
May he RIP, and lets hope that the RAF pin the problem down and publish the true cause of his death, and do not simply put it down to pilot error as is so often the case, and an easy way out for them.