You Should Install the FLAT Spring!
LCPiper...
I have alot of experience working through problems with my 238, discussing them with Sig Customer Service, etc. It sounds like you purchased a gun that was manufactured and distributed prior to the availability of the updated, FLAT spring. I strongly encourage you to install and use the new flat spring when you receive it. I guess it would be comforting to know that your 238 works well without it, but from what I have learned from Sig, that new flat spring is a key factor in "fixing" this pistol. Personally, I wouldn't have confidence in my P238 without it.
Also...yes, by all means, keep it clean and oiled. During every few range trips, based on Sig's recommendation, I break down the gun and put a couple drops of Militec-1 gun oil on the rails, then re-assemble and shoot a couple mags (to get the rails hot and help the Militec-1 bond with the metal). This helps maintain lubrication, even when the rails are otherwise "dry" (not dripping wet from a recent cleaning/lubing). Once you are familiar and practiced with the break-down and re-assemply process, you can do this in 60 seconds and be shooting again.
For me, these four factors have resulted in owning a P238 that runs very smoothly and without any further failures...
1) New updated flat spring.
2) New updated magazine.
3) Clean the gun after every range trip with Rem Oil
(or your own favorite gun oil)
4) A couple drops of Militec-1 on the rails, during range sessions, every few trips.
The first two factors above are simple, one-time fixes.
The last two are really just basic care of any pistol.
With the new fixes and basic pistol care, in my opinion, there is no longer any reason to shy away from this excellent CCW pistol, if the caliber and other features of the gun happen to appeal to you.