Hi there,
OK, looks to be correct. 
Definitely a stranger things occurence not the norm AFAIK, SMH 
You would have had to hooked the debuggers 5V ref or USBVCC to the Xiao’s SWD 3V3 (only electrical way I see that happening) If you were in Source mode the the 500ma. should be enough and then some, asking too much of the Xiao to power the Debugger and the Expansion board maybe ?? (elephant and a Rino= Elifino 
)
I have a Toasted XIAO 
, but it works except the Battery Charger doesn’t work anymore.
Does the MG24 device still charge a battery ?
HTH
GL:-) PJ 
FYI:
Specifications
Product specifications , If in the wrong mode ? (reaching 
)
4. Power Supply Modes The Simplicity Link Debugger is powered when connected to an host by the USB cable. When powered, the Simplicity Link Debugger can operate in two modes: 1.Sensing mode (default): the Simplicity Link Debugger senses the supply voltage of the connected device. In this mode, the current absorbed by the sensing circuitry of the debugger from the connected device is typically less than 1 µA 2.Sourcing mode: the Simplicity Link Debugger sources a fixed voltage of 3.3V to the device being debugged At start up, the Simplicity Link Debugger operates in sensing mode (default). This mode is intended for self-powered devices , i.e. the connected board has its own power supply or battery.
Another Dev has two units, the first one is very flaky with the Power switch(modes) if you press it too long it switches from Source to Sink ?
he likes it too btw but moans about the Software … LOL 