In the first save I tried setting the fling distance it worked fine, but whenever I try to do it on my newer saves I get this error https://imgur.com/a/jxnyY2d

In the first save I tried setting the fling distance it worked fine, but whenever I try to do it on my newer saves I get this error https://imgur.com/a/jxnyY2d
I tested a bit, I only have the issue, if the inserter has yet to be placed, while I'm changing the distance. Placed ones work fine.

Just to test, try copying any buildings/machines with ctrl+c, then try again to adjust inserter before placing. If it works without crashing, then I know what the problem is.

Yep, it worked. Seems like you're right. Thanks!

Okay, that means I have to make a temporary blueprint for players if they haven't used copy in a save before. Thanks for the report 😀