The loader mod used is Loaders Modernized

Exception at tick 96946630: The mod Lane Filtered Loaders (1.1.17) caused a non-recoverable error.

Error while running event lane-filtered-loaders::on_built_entity (ID 6)
lane-filtered-loaders/control.lua:85: attempt to index global 'new_entity' (a nil value)
stack traceback:
lane-filtered-loaders/control.lua:85: in function 'replace'
lane-filtered-loaders/control.lua:160: in function <lane-filtered-loaders/control.lua:157>

strange, it only crashes when i do it manually, making bots do it works using an upgrade planner

hmm i also had the same crash when i accidentally try to replace the same iper-loader twice by double clicking

ALL ISSUES are being fixed in a unified loader mod, since in 2.0.65 Wube added a new loader property (respect insertion limit) and trying to manage 3 possibly interconnected mods is not worth the trouble. I will send a message here and update these mods accordingly once that combined loader mod is released.