It is not a bug, usually (not in your case look at bolded text)all this means is that even though you have enough msar at the time, if you were to respawn you would not have enough to pay for your loadout. Whenever you rank up, you get more msar and your msar levels are fully filled, if you make a loadout that costed 180/180 of your msar on top of your default loadout, you would not be able to spawn because it would be 180 msar + your default kit that you spawned with which is greater than your limit. IN YOUR CASE, it looks like you are private, if you spawn as driver(like you did), the weapon that you spawn with actually requires corpral to purchase from an arsenal, being the full auto m16 that only the driver and special forces spawns with. Hence it is too high of a rank item for you to save as a private.

Thanks for reply, but I did not spawn as a driver. I created a recon squad. But from what you say - the save option is totally useless in my case then.

It has to be a driver because of your msar being 56/80. this happens a lot because if you were in a transport squad, then created a recon squad and spawned, it will keep the driver kit as your spawn unless you changed it in the spawn menu. Also because of the hat as well.

I joined game. Created squad of recon and spawned.