The latest version of the mod (I specifically deleted and reinstalled it), I have never even seen the chainsaw itself, but I have already seen this error more than once.
There are no incompatible mods installed either, but there are a lot of mods.

`function: AZ_Chainsaw_render -- file: AZ_Chainsaw_tooltip.lua line # 27 | MOD: Authentic Z
function: render -- file: InventoryUI.lua line # 21 | MOD: Starlit Library
function: render -- file: Skill Recovery Journal Tooltip.lua line # 296 | MOD: Skill Recovery Journal
function: render -- file: KATTAJ1_TooltipFixer.lua line # 13 | MOD: KATTAJ1 Clothes Core
java.lang.RuntimeException: Object tried to call nil in AZ_Chainsaw_render
at se.krka.kahlua.vm.KahluaUtil.fail(KahluaUtil.java:101)
at se.krka.kahlua.vm.KahluaThread.luaMainloop(KahluaThread.java:817)
at se.krka.kahlua.vm.KahluaThread.call(KahluaThread.java:174)
at se.krka.kahlua.vm.KahluaThread.pcall(KahluaThread.java:1826)
at se.krka.kahlua.vm.KahluaThread.pcallvoid(KahluaThread.java:1668)
at se.krka.kahlua.integration.LuaCaller.pcallvoid(LuaCaller.java:38)
at zombie.ui.UIElement.render(UIElement.java:2009)
at zombie.ui.UIManager.render(UIManager.java:419)
at zombie.gameStates.IngameState.renderFrameUI(IngameState.java:1332)
at zombie.gameStates.IngameState.renderframeui(IngameState.java:1318)
at zombie.gameStates.IngameState.renderInternal(IngameState.java:1457)
at zombie.gameStates.IngameState.render(IngameState.java:1407)
at zombie.gameStates.GameStateMachine.render(GameStateMachine.java:28)
at zombie.GameWindow.renderInternal(GameWindow.java:476)
at zombie.GameWindow.frameStep(GameWindow.java:948)
at zombie.GameWindow.mainThreadStep(GameWindow.java:647)
at zombie.MainThread.mainLoop(MainThread.java:76)
at java.base/java.lang.Thread.run(Unknown Source)
`