This has been reported in pharo fork as https://github.com/pharo-project/opensmalltalk-vm/issues/179 and also affects upstream opensmalltalk-vm

``` | result obj | result := OrderedCollection new. obj := { 1. 2. 3 }. result add: (thisContext objectSize: obj). "Should be 3" obj become: { 'a'. 'b'. }. result add: (thisContext objectSize: obj). "Should be 2, but is 0" Smalltalk garbageCollect. result add: (thisContext objectSize: obj). "Should be 2" result "an OrderedCollection(3 0 2)" ```