Thanks for the offer! We'll test it first with an IG account and since you got it this often, we should be able to reproduce it here. Otherwise we'll send you a special bridge version with some diagnostics output. Either way I think we'll find out soon what happened.

I still had these duplicates on a regular basis but not much time to further diagnose ... Now I restarted Z12 using a fresh 1.60.1 installation - and again duplicates after just a few days:

Trade ID Lots Entry Time Entry Price Stop Trail Target Risk Profit Pips
[AUD/USD:NET:L8864] 8078864 31 07-28 08:19 0.7968 0.7969 0.5578 - - - - - - - - -6334$ -0$ -0.1p
[EUR/USD:NET:L0742] 8090742 18 07-28 16:19 1.1747 1.1857 0.8223 - - - - - - - - -5402$ 166$ 108.1p
[NAS100:NET:L1665] 8131665 7 08-01 08:19 5914 5912 4140 - - - - - - - - -10508$ -19$ -31.9p
[NAS100:NET:L6937] 8136937 3 08-01 12:19 5900 5912 4130 - - - - - - - - -4499$ 27$ 107.6p
[GBP/USD:HP:S7153] 8157153 8 08-02 01:46 5943 5911 1.8481 - - - - - - - - +40243204$ -189$ -278.9p
[NAS100:NET:L7153] 8157153 7 08-02 04:19 5943 5912 4160 - - - - - - - - -10562$ -189$ -319.1p
[USD/CAD:HU:S0357] 8170357 19 08-02 15:26 1.2545 1.2562 1.7563 - - - - - - - - -6427$ -23$ -18.0p
[AUD/USD:NET:L1156] 8171156 32 08-02 16:19 0.7979 0.7968 0.5585 - - - - - - - - -6459$ -31$ -11.4p
[USD/CAD:NET:S1157] 8171157 31 08-02 16:19 1.2550 1.2562 1.7570 - - - - - - - - -10458$ -28$ -13.6p
{AUD/USD:CT:l9802} 69802 31 07-28 08:19 0.7968 0.7969 0.7706 0.8230 - - - - -697$ 2$ 0.6p
{EUR/USD:CY:l0004} 70004 18 07-28 16:19 1.1747 1.1857 1.1828 1.1886 - - - - +122$ 166$ 108.3p
{USD/CAD:CY:s0105} 70105 19 07-31 00:19 1.2481 1.2562 1.3003 1.1959 - - - - -681$ -109$ -83.9p
{GBP/USD:BB:s0606} 70606 36 07-31 20:19 1.3194 1.3226 1.3366 1.3022 - - - - -528$ -102$ -33.6p
{NAS100:VO:l0908} 70908 7 08-01 08:19 5914 5912 5828 6000 - - - - -516$ -20$ -33.2p
{NAS100:HU:l1009} 71009 3 08-01 12:19 5900 5912 5609 6191 - - - - -741$ 27$ 106.8p
{NAS100:VO:l1410} 71410 7 08-02 04:19 5943 5912 5856 6029 - - - - -516$ -189$ -320.0p
{GBP/USD:HP:l1611} 71611 28 08-02 12:19 1.3231 1.3226 1.2936 1.3526 - - - - -702$ -15$ -6.4p
{USD/CAD:HP:s1712} 71712 31 08-02 16:19 1.2550 1.2562 1.2881 1.2219 - - - - -695$ -31$ -14.8p
{AUD/USD:HP:l1713} 71713 32 08-02 16:19 0.7979 0.7969 0.7720 0.8238 - - - - -703$ -32$ -12.0p

In MT4, 8157153 is the NAS100 trade (0.07 long) while GBP/USD is 8155548 (0.08 short).

To summarize:
o MT4 statement
- GBP/USD 8155548 is only visible as an open trade, 0.08 short.
- NAS100 8157153 is only visible as an open trade, 0.07 long
o Zorro\Log\trades.csv
- HP,Short,GBP/USD,8157153,19,2017-08-02 01:46,2017-08-02 12:19,5942.60,5933.40,-38.31,0.00,Reverse
o Zorro\Log\Z12real.log
[...]
[Wed 17-08-02 00:19] 11598 +360 +378 //// 1.1801/1.18141.1800/1.1810
[...]
{GBP/USD:HP:l9701} Stop 27@1.32010: +277$ at 01:46:41
Entr 1.3080 Exit 1.3201 Spr 0.0001 Slp -0.20$ Rol 0.54$ Com 1.62$
Enter 27S GBP/USD Stop 0.4548 at 01:46:41.
[GBP/USD:HP:S5548] Short 27@1.32010 Pool trade at 01:46:41
Stop: 1.8481 Trail: 0.0000 TakeProfit: 0.0000
[...]
[Wed 17-08-02 04:19] 11686 +360 +465 //// 1.1810/1.18291.1794/1.1823
Enter 1L NAS100 Stop 86.2268 Trail 86.2268 at 04:19:01
{NAS100:VO:l1410} Long 7@5942.60 Risk 522$ ts at 04:19:01
Stop: 5856.3730 Trail: 6028.8271 TakeProfit: 0.0000
Enter 7L NAS100 Stop 0.4531 at 04:19:01.
[NAS100:NET:L7153] Long 7@5942.60 Pool trade at 04:19:01
Stop: 4159.8203 Trail: 0.0000 TakeProfit: 0.0000
[...]
[Wed 17-08-02 12:19] 11485 +360 +265 ////\ 1.1834/1.18681.1819/1.1829
[...]
[GBP/USD:HP:S7153] Cover % 19@1.32309: -38.31 at 12:19:01
Entr 5942.6001 Exit 5933.3999 Spr 0.0001 Slp 0.32$ Rol 0.00$ Com 0.48$

But I guess you need to see all the phantom trades, too?
I can provide Zorro's logs and an MT4 Detailed Statement for diagnosis, if needed... where to send it to?
I will even leave both trades open for now as I'd like this to be fixed as soon as possible.

Thanks.

Please contact support(at)opgroup.de, they'll look into it.

Support quickly found the root cause in MT4 and already provided a modified version of the plugin supposed to work around the issue. I'm really impressed. Testing now ...

So far no more duplicates. But now IG have a problem with all MT4 accounts, no trades can be opened for several instruments. IG support told me it would last for another few hours, at least. For some accounts even until tomorrow ...

The problems @ IG were related to the transition to "Limited Risk" for all accounts by default. This is now completed (at least for my account) but leading to new serious issues for system traders, see this post..

So far no more duplicates despite several partially closed trades. I assume the modified MT4 plugin will become part of the regular Zorro distribution? If yes, from which version onward?

From 1.62 on. But it is already in the beta version and can also be download from the bugs list.