I am experiencing a very strange crash, here is the backtrace.

* thread #1: tid = 0x2403, 0x3379516c CoreFoundation`CFHash + 8, stop reason = EXC_BREAKPOINT (code=EXC_ARM_BREAKPOINT, subcode=0xdefe)
    frame #0: 0x3379516c CoreFoundation`CFHash + 8
    frame #1: 0x33797a9c CoreFoundation`CFBasicHashRemoveValue + 1408
    frame #2: 0x337974ee CoreFoundation`CFDictionaryRemoveValue + 166
    frame #3: 0x3420988e Foundation`-[NSISEngine removeConstraintWithMarker:] + 562
    frame #4: 0x34211dbe Foundation`-[NSLayoutConstraint _removeFromEngine:] + 230
    frame #5: 0x35a954ec UIKit`-[UIView(UIConstraintBasedLayout) _layoutEngine_willRemoveLayoutConstraint:] + 44
    frame #6: 0x358488fc UIKit`__48-[UIScrollView _setAutomaticContentConstraints:]_block_invoke_0 + 148
    frame #7: 0x34208882 Foundation`-[NSISEngine withAutomaticOptimizationDisabled:] + 166
    frame #8: 0x35848838 UIKit`-[UIScrollView _setAutomaticContentConstraints:] + 116
    frame #9: 0x35848e6c UIKit`-[UIScrollView _rememberDependentConstraint:] + 112
    frame #10: 0x35a9e3ae UIKit`___updateViewDependenciesForConstraint_block_invoke_0 + 30
    frame #11: 0x35a954ba UIKit`_updateViewDependenciesForConstraint + 202
    frame #12: 0x35a953da UIKit`-[UIView(UIConstraintBasedLayout) _layoutEngine_didAddLayoutConstraint:roundingAdjustment:mutuallyExclusiveConstraints:] + 154
    frame #13: 0x35a95534 UIKit`-[UIView(UIConstraintBasedLayout) _tryToAddConstraintWithoutUpdatingConstraintsArray:roundingAdjustment:mutuallyExclusiveConstraints:] + 36
    frame #14: 0x3567c2e0 UIKit`-[UIView(Internal) _didMoveFromWindow:toWindow:] + 376
    frame #15: 0x356d34fe UIKit`-[UIScrollView _didMoveFromWindow:toWindow:] + 50
    frame #16: 0x3567c5c6 UIKit`-[UIView(Internal) _didMoveFromWindow:toWindow:] + 1118
    frame #17: 0x35676e52 UIKit`-[UIView(Hierarchy) _postMovedFromSuperview:] + 138
    frame #18: 0x3565e7dc UIKit`-[UIView(Internal) _addSubview:positioned:relativeTo:] + 1300
    frame #19:
ios autolayout
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