We have the following problem:

• Mongo cluster consists of 6 shards deployed to AWS EC2
• One of the collections started to behave very slow for the aggregation queries. We added appropriate indexes, but it continued to be messed up
• We wanted to dump it and restore in the local environment to test our approach
• Dump worked, but restore fails - so we are stuck

Error stack trace looks like this:

2014-11-01T19:14:42.037-0700 Progress: 2821305158/3003237478 93% (bytes)
2014-11-01T19:14:45.002-0700 Progress: 2850985158/3003237478 94% (bytes)
2014-11-01T19:14:48.000-0700 Progress: 2881247558/3003237478 95% (bytes)
2014-11-01T19:14:51.006-0700 Progress: 2910681158/3003237478 96% (bytes)
2014-11-01T19:14:54.032-0700 Progress: 2939801158/3003237478 97% (bytes)
2014-11-01T19:14:57.058-0700 Progress: 2967957958/3003237478 98% (bytes)
2014-11-01T19:15:00.002-0700 Progress: 2996383558/3003237478 99% (bytes)
2014-11-01T19:15:00.747-0700 Assertion failure amt == (size_t)( size - 4 ) src/mongo/tools/tool.cpp 330
2014-11-01T19:15:00.765-0700 0x1006b822b 0x100670e12 0x100661a92 0x100657d10 0x10000a187 0x10000ccf7 0x10000c7a1 0x10000c7a1 0x10000c7a1 0x10000f7fc 0x100657621 0x1006596cd 0x1006599d2 0x100000df4
0 mongorestore 0x00000001006b822b _ZN5mongo15printStackTraceERSo + 43
1 mongorestore 0x0000000100670e12 _ZN5mongo10logContextEPKc + 114
2 mongorestore 0x0000000100661a92 _ZN5mongo12verifyFailedEPKcS1_j + 274
3 mongorestore 0x0000000100657d10 _ZN5mongo8BSONTool11processFileERKN5boost11filesystem34pathE + 1450
4 mongorestore 0x000000010000a187 _ZN7Restore22processFileAndMetadataERKN5boost11filesystem34pathERKSs + 4191
5 mongorestore 0x000000010000ccf7 _ZN7Restore9drillDownEN5boost11filesystem34pathEbbbb + 3109
6 mongorestore 0x000000010000c7a1 _ZN7Restore9drillDownEN5boost11filesystem34pathEbbbb + 1743
7 mongorestore 0x000000010000c7a1 _ZN7Restore9drillDownEN5boost11filesystem34pathEbbbb + 1743
8 mongorestore 0x000000010000c7a1 _ZN7Restore9drillDownEN5boost11filesystem34pathEbbbb + 1743
9 mongorestore 0x000000010000f7fc _ZN7Restore5doRunEv + 10140
10 mongorestore 0x0000000100657621 _ZN5mongo8BSONTool3runEv + 165
11 mongorestore 0x00000001006596cd ZN5mongo4Tool4mainEiPPcS2 + 1437
12 mongorestore 0x00000001006599d2 main + 66
13 mongorestore 0x0000000100000df4 start + 52
assertion: 0 assertion src/mongo/tools/tool.cpp:330

We can provide actual dump file upon request - it's 865MB