virtual machines: what exactly is a TX collision in the context of a virtual machine?

I am inspecting a problem with a set of MongoDB replicas that reselects a primary several times per minute. There seems to be something wrong with the network configuration, but I still can't pinpoint it.

When you run ifconfig in the virtual machine of one of the nodes, I see a lot of TX collisions in eth0:

RX packets 850479  bytes 253445128 (241.7 MiB)
RX errors 0  dropped 12070  overruns 0  frame 0
TX packets 512851  bytes 210486965 (200.7 MiB)
TX errors 0  dropped 0 overruns 0  carrier 0  collisions 2648104

I do not understand what it means.

When I look for exactly what TX collisions are, all I find is that they are related to real physical network cables. However, the hardware server that hosts this virtual machine reports zero collisions

So what exactly is a TX collision in a virtual machine context (a Debian 9 running on QEMU / KVM, hosted on Ubuntu 18, if it is important)?