As title, there was this connected and powered HV wire, after I broke one of the connector and
all the expected items (a connector and two wires) are dropped, I walked in a space where it once was and died instantly
I've tried putting a block and break it, but still got killed, I also got killed in one hit instead of two (as it should only deal 7 heart/hit)

Version:
IE: 0.12-89
Forge: 1.12.2-14.23.5.2818

Try updating IE to build 91. There's a chance a fix I added in 90 will apply to this situation as well as to many others.