Too many shavings means too high a carbon to nitrogen ratio. I've got to the end of the season and still found shavings in the soil. The shavings rob the soil of nitrogen until they're rotted. I've had this happen enough times to know that it isn't just theory! If I had manure with a lot of shavings I'd stack it for several months to rot down. Fresh strawy horse manure can be ready in a few weeks if the weather isn't too cold. All good, but needing different treatment! It's the same with leaves - they need stacking for a year or more as they're low in nitrogen but high in carbon. A very good thing to do with high-carbon organic matter is to mix it with fresh grass clippings. The nitrogen in the clippings gets the bacteria going nicely so you don't have to wait forever for the fungi to do their job. I do this with my leaf mould and it's ready in six months instead of years. Bob Flowerdew calls it accelerated leaf mould. It's brilliant stuff for the raspberries and spuds as it keeps the pH down and the mulch keeps the weeds at bay.