During the bring-up of the machine, it occurred to me, that charging or supplying the tablets via the USB OTG micro-A jack should be monitored more closely.
Many current and voltage monitoring devices are around. An inexpensive type will do. The device selected alternates cyclically between displaying current and voltage.
The clamshell case can be opened easily, e.g., by using a Xacto knife.
Due to their contact resistance, pluggable connectors are to be avoided. So they have been desoldered. All power connections have been made of wire with a sufficient cross-section.