Crusader levels are limited by 5000. If you go over it, either by hacking them directly or by hacking the cash and levelling manually you get that error. Be VERY careful with "max all levels" button, if you have over 1e150 cash it will push Bushwhacker over 5k levels and error you.

Doesn't seem to work?
Ohwait. It does work, but wonky.
ADDING a bunch of buffs does NOT work. The number resets to the un-cheated after reloading the game.
Spam does work, but all the warps of the quality you spammed will be gone after reloading.
Spammed up loot, like event pies, remains in your possession.

Maybe edit your hack to clarify the issue of what works and what doesn't?

The developers are REALLY nice people. There are a ton of people posting on the forums that they are stuck with "Uh oh!" message, even admitting about playing with CE, and the devs just reset the broken values when asked, I think not even wiping your whole save like most would've done.
Soo try that.

Pies are 4bytes x8+6, I think. 
It doesn't work anyway.

In order to get a truckload of pies, search for your timewarp card (blue rarity works best as its warp big enough but common enough for you to get some from chests quickly) amount, freeze it and then autoclick spam the everloving crap out of it. This will get you your pies. Like, a million or two and a half.

Then go buy event chests with them.

i find that hacking the gold is enough to grind idols and do the challenges

the event candies, i get by using what Doken and amoon mentioned

i don't need speedhack (which sometimes makes the game go out of synch and forces you to refresh the game), also don't need to tweak the crusader levels or insta kill or ability cooldown or dps hack since having enough gold and idols takes care of these without having to hack

one thing that doesn't seem to be working for me is the Each Chest box thingy which people have talked about. i followed the suggestions to get it to work and according to my CE, i was able to reset the highest level reached number to 1 before i did the reset and even after just as the suggestions here state, but in the end, i never got chests after every boss and i never got the jewel chest at the second boss like the hack is supposed to give me

Martygalez: you can x5 speed pretty safely. The out of sync errors still pop up but they resolve after a couple seconds.

Events allow easy farming of event jewel chests in extremely high amounts, you can get hundreds of them without seriously trying.

You can farm silver chests in huge amounts anytime tho. Regular Jewel chests are not so easily farmable.

For those who got locked with uh oh.

I used Fiddler Web Debugger to intercept and change the savefile to fix the broken lvls

This could be used to change lots of things... but i asked on steam forums to be unlocked, but got impatient. So i'll leave my save alone for a while.

Fyi here is a editedsample

current_area":297,"highest_area":301,"normal_loot_chests":21,"rare_loot_chests":0,"gold":"7.77982412296902e+77","heroes":[{"hero_id":1,"level":2002,"upgrades":[125,6,5,3,4,2,8],"health":2008,"grind_time":12,"disenchant":156,"owned":1,"in_seat":1},"loot_id":239,"count":1},{"loot_id":243,"count":1},[{"buff_id":1,"remaining_time":0,"total_duration":0,"inventory_amount":20},{"buff_id":2,"remaining_time":0,"total_duration":0,"inventory_amount":21},{"buff_id":30,"remaining_time":0,"total_duration":0,"inventory_amount":0},{"buff_id":31,"remaining_time":0,"total_duration":0,"inventory_amount":0},{"buff_id":32,"remaining_time":0,"total_duration":0,"inventory_amount":0},{"buff_id":33,"remaining_time":0,"total_duration":0,"inventory_amount":0}],"stats":{"objective_previously_completed":"0","rare_chests_bought_premium":"10","rare_generic_chests_bought_premium":"30","crusaders_recruited":"4535","last_daily_quest_time":"1457031079","ability_bar_shown":"1","ad_bonus_protip_seen":"1","bench_protip_seen":"1","boss_defeats":"708","boss_defeats_on_highest_level":"621","boss_kills":"21172","buff_inventory_shown":"1","candy_canes_spent":"30300","c

Didnt find a guide. I worked it out by messing around
Basicly you need to get a breakpoint on the post response that contains the lvls using rules, Then quickly change it and send it to the games before it timesout. 

Running on 20x speed without problems all the time. The only problem i have is i always get the "uh oh" message at wave 1300+ if i run it with instant kill (highest was 1,5k long time ago) anyone else got this problem?