Beware the effects of changing security symbols

I don't understand what happened, but will caution you all. My wife and I have data for 27 investment accounts with 80 years of history in QW2014. Seven of them are active and are reconciled each month. Our security list contains a bit over 525 securities, (tried to count on the screen instead of printing), of which about 150 had no recorded symbol, only the name. (I do not download transactions or prices, so this has not been a problem.)

After reconciling active accounts for June of this year, I decided to work on getting symbols fixed because the QIF export will not export the price history without them. I did already have about 30 fake symbols I have created for assets that I treat as investments, such as insurance which pays dividends and interest. I believe my fake symbols are fairly safe as I just created a sequence with my initials and a number, such as CRC01, CRC02, etc. Some of these have been in my data for years with no problems. Others I researched online and even found symbols for securities that no longer exist in the markets.

After I had done about 100 of the securities, I looked at my investment accounts in detail and found a scary thing. While all of the month-end account values seem to be correct, there are some strange figures that stand out in the gain/loss column of the Holdings view.

From one account for example, I see one security with a gain/loss of $-35,610.64 and three rows down another with a gain/loss of +$40,153.24. These are nowhere near accurate. Reviewing the price history detail, I don't see any large prices recorded in error. What I do see is that the number of shares for both securities in Holdings now are invalid by very large numbers in the hundreds.

Fortunately, I do have 13 backups for the month, so now the challenge is finding the one after I reconciled which I hope is before I began changing symbols.

I have no idea how this could occur as the identifying data elements seem to be security name and security symbol so you would expect that incorrect merging of price history would have altered the account totals and it is mind-blowing that the month-end account total values are still correct.