Nooe it’s not normal. Check if your dashd does not lag with blocks, is fully synced and is on the newest v19 version too.
As @splawik21 said, it is not worth PoSe ban to save on server cost by using a cheaper low-resource one. Instead of 2GB RAMtry something larger like 6GB, and 3+ CPU cores. Also, your VPS provider might sometimes have down-time, in which case the Dash network will not be able to see it. So use a high-quality provider, and don't choose the lowest specification VPS.
- Bugs in the core node code, we've seen a lot of those in v18 and v19 and tried to fix them all, others may still exist.
- The node is actually off-line.
- The network our VPS is on is off-line.
- Routing issues on the internet.
- The node you are talking to has for some reason 'discouraged' your node ie, it no longer listens to you and thus misses your reply and THEN scores you! We see a LOT of this on testnet.
- Some VPS providers purposely firewall certain networks, I know that coins.host for example F/W traffic between other VPS's on their own network!
- Your node is online, but not at the current tip.
- Your node is online, but severely resource constrained, eg CPU and is SLOW to respond. This can be a fleeting occurrence, since the load on dashd is not constant and if you are using a shared instance it could even be because someone else's VPS is suddenly super busy and drains CPU resources from your own instance !
- Your protx is revoked - Obvious and easy to remedy.
- Your collateral is spent, instant ban.
- You are running a software F/W on your VPS that is interfering or has a rate limit.
- VPS is doing a reboot.
- Malicious nodes? Note that to score a node, it must be voted by others in the quorum too, how many exactly, I don't know. Large operators are incentivised to attack smaller operators, this should be obvious.
- The rogue node, a node that thinks it is synced to tip and erroneously votes to score others that are actually properly synced up.
- etc etc etc.