Bank to M-PESA transactions have unusually high failure/reversal rates. That's what I noted from operating an NIC bank account. This has been the case even before the M-PESA service was relocated to Kenya.
Some PayPal transactions have been affected by how some card providers effected their CHIP-n-PIN technology. If your card explicityl asks for the PIN at all times (e.g the Airtel VISA card), then hard luck!
To those who may be affected, Barclaycard & Barclays Bank are two different entities, factor in some payment reconciliation latencies when using your BBK online banking platforms for transactions involving your Barclaycard Credit Cards.