I think part of the problem is people's unwillingness to ride at the front of the group. Whether this is a lack of confidence or being unwilling to take 'a turn', I don't know. Also as Steven has commented closing gaps down, in the chain, can be an issue. This could be due to lack of concentration, fearing riding too close to the wheel in front or a fitness issue.
I will make a point of discussing how the group should ride, before the start of the club run and try and 'encourage' all riders to keep in formation.
Coaching group riding will help BUT I cannot do this out on the road, while riding with the group.
The coaching has to be done as a formal coaching session, which I am more than happy to do, maybe on a Saturday afternoon if anybody is interested.
I will be doing a novices ride on November 11th but would be able to fit in a session on any other Saturdays in November