The HDMI socket of my small laptop (Acer Aspire ES1-131) is connected directly to the main board, I gather.
The old HDMI-to-VGA adapter was self powered from the HDMI cable, or could be powered by a 5v USB supply. Hitherto I didn't need to power it from a 5v supply, but will probably power the new one that way, in case the current load to power it was the cause, although I frankly doubt it. The power required is surely miniscule - and in any case, HDMI cables are supposed to be hot-pluggable.
Personally I reckon that the problem was probably as Jhieminga suggests and is a design issue with that model of laptop which has rear mounted HDMI, USB and power sockets.
Hopefully the replacement (Lenovo 100S), which has a side mounted HDMI socket, will cope OK.