This is because they have been sliding in his shoes as he has been walking. This has become clear from observation and testing my feet in his shoes with them in.
Unfortunately, at the moment Fela only has one full size pair of orthotic insoles (hard with blue underneath) which have been moved to his BLUE trainers which he tends to use the most.
A new pair have been ordered from the Orthotics clinic and should soon be delivered. In the meantime, if Fela is about to wear another pair of shoes, these insoles will need to be transferred to them. The exception are his sandals which do not require insoles.
Thank you for your co-operation!