Hi altech,
A few thoughts - do with them as you think best
That the socket pulled out so easily does not bode well for the unit's build quality.
There are reports/anecdotes online suggesting Mishto units are unsafe, even potentially deadly. See for example
https://forums.whirlpool.net.au/archive/2318966
Once all over ebay - now try a search for Mishto inverters - none! There's a message in that I reckon.
If it were mine I'd bin it after giving it a good belt with a large hammer to ensure no-one else scavenged it & used it.
On another tack - What do you need such a large rated (3000w) inverter for? - what are you planning to power with it? It seems relatively common that folk in 4x4 circles when fitting inverters seem to go for the biggies, which makes little sense in most instances given that few 4x4's have sufficiently large battery banks to make use of them. Most have a single aux, or maybe 2. I have 3 x 120AH aux batteries & wouldn't dream of connecting a 3000w inverter to them! If using them to power lower wattage appliances it's not uncommon for these large inverters to use as much of your battery's resources to run themselves as they do to run your appliances. Unless a solar system has a large &/or lithium battery bank, & sufficient resources to recharge within a 24 hour period it is at best, in my view wasteful & inefficient use of limited battery power & at worst a surefire battery killer. If you do have a large enough/suitable battery bank & re-charging system then I guess you could run all sorts of 240v power tools, toaster, espresso machine, maybe even air conditioning ..... but if I were doing any of those things I'd sure want a decent quality inverter I felt confident wasn't going to kill me.