ReillyBrogan Yes. You are right. It was some pisi CDN update, I forgot which. (checked: from 25/4.)
However I meant to relate to a chat long held in the channel, with an output added, which I had no idea (as a newbie) why it did not work initially then that way, but later the replacement was held as should, and I wondered why, not being a programmer. The details I don't remember but the system.base error also appeared then.
Reference
https://dev.getsol.us/R2442:ef46fb7dd247612f67bce7ad67631669efd36939
Probably no matter. (chat was 17/6 on Support I think, but it probably doesn't matter anymore)