R.A.F. Crashes in Scotland during WWII

My late father told me this over 30 years ago and I wondered if I could find anything about it.
He was working in the north of Scotland at Forres on construction of buildings on the airfield. He said there had been several unexplained crashes and as in such a close environment he lost several friends. He had been offered flights to as near to Greenock as they could get in his long weeknd off as the rail journey was a nightmare but he didn't take them up on it he told he me was really upset because that plane crashed too.
One morning whilst he was working on the roof of one of the temp huts he was building he saw a covered truck pull up at the far side of the airfield, and he watched while several of the ground crew who were Poles were put in it and driven out of the airfield, he didn't think to much of it and it wasn't until later in the evening in the mess he was told that they had found the cause of the planes crashing and if he wanted to go on any flights home on his leave weekends no problem. Naturally my dad asked what the cause was and he was told sugar in the fuel and the matter had been dealt with.
Over the years when talking about the war he told me this several times, and I can quite honestly say he wasn't one for flights of fancy and had the most excellent memory, now I wish I had written down his experiences.
I looked up crashes in the area of Forres and Kinloss and there are a few I just wondered if any one else had heard of such an occurrance.

If i have bored you all to death I do apologise!