Multi line cursors cause heap exhaustion

[ethanxxxl]

When I use multiple cursors relatively extensively, eventually Lem crashes and spits out this error:

Heap exhausted during allocation: 81100800 bytes available, 652147216 requested.
     | Immobile Objects |
 Gen layout symbol   code  Boxed   Cons    Raw   Code  SmMix  Mixed  LgRaw LgCode  LgMix Waste%       Alloc        Trig   Dirty GCs Mem-age
  1      0      0      0      2     12      2      0      3      6  23885      0      0    0.1   782921008    10737418   23888   0  0.3895
  2    113      4    117     51     30     17      1      5     21   1212      0      0    1.5    43158416     2000000    1233   0  0.0000
  3      0      0      0      0      0      0      0      0      0      0      0      0    0.0           0     2000000       0   0  0.0000
  4      0      0      0      0      0      0      0      0      0      0      0      0    0.0           0     2000000       0   0  0.0000
  5      0      0      0      0      0      0      0      0      0      0      0      0    0.0           0     2000000       0   0  0.0000
  6   4031  31373  47806    810    630    288     26    106     88     51      0    106    2.8    67044688     2000000      35   0  0.0000
Tot   4144  31377  47923    863    672    307     27    114    115  25148      0    106    0.4   893124112 [83.2% of 1073741824 max]
GC control variables:
   *GC-INHIBIT* = false
   *GC-PENDING* = true
   *STOP-FOR-GC-PENDING* = false
Collection trigger variables:
   dynamic_space_size = 1073741824
   bytes_allocated = 893124112
   auto_gc_trigger = 946811203
   bytes_consed_between_gcs = 53687091

I haven't done extensive testing to see what the root cause is, but it has happened a few times so far, maybe someone can replicate?
I was using C-mode and covering large areas with multiple cursors to insert comments/change indentation. (about 70-80 lines at a time).

The crash didn't happen all at once probably after 5-10 operations.