Hola Theliel, gracias por tu extensa respuesta, me quedan bastante claros los conceptos que comentas.
He seguido haciendo pruebas, como activar el upnp como indicabas e incluso abrir manualmente más puertos y el juego sigue funcionando mal con el nuevo router.
También he hecho algunas pruebas más con WinMTR y he visto algo curioso que no sé si es destacable o es normal, cuando configuro el programa para que haga ping en intervalo de 1s todo se ve correcto:
|------------------------------------------------------------------------------------------|
| WinMTR statistics |
| Host - % | Sent | Recv | Best | Avrg | Wrst | Last |
|------------------------------------------------|------|------|------|------|------|------|
| 192.168.1.1 - 0 | 1104 | 1104 | 0 | 0 | 9 | 0 |
|239.red-81-46-38.customer.static.ccgg.telefonica.net - 0 | 1104 | 1104 | 2 | 9 | 108 | 2 |
|169.red-81-46-45.customer.static.ccgg.telefonica.net - 0 | 1104 | 1104 | 2 | 7 | 107 | 3 |
|245.red-81-46-45.customer.static.ccgg.telefonica.net - 1 | 1088 | 1084 | 2 | 8 | 145 | 3 |
| 1.red-80-58-78.staticip.rima-tde.net - 0 | 1104 | 1104 | 3 | 8 | 110 | 4 |
|xe-7-1-2-65-graarctw1.net.telefonicaglobalsolutions.com - 1 | 1100 | 1099 | 10 | 15 | 116 | 11 |
|valve-be40-grtmadix2.net.telefonicaglobalsolutions.com - 0 | 1104 | 1104 | 11 | 14 | 115 | 12 |
| 155-133-246-212.valve.net - 0 | 1104 | 1104 | 10 | 14 | 115 | 12 |
| 155-133-246-50.valve.net - 0 | 1104 | 1104 | 9 | 14 | 115 | 10 |
|________________________________________________|______|______|______|______|______|______|
WinMTR v0.92 GPL V2 by Appnor MSP - Fully Managed Hosting & Cloud Provider
Pero cuando subo la intensidad, a 0.5s
|------------------------------------------------------------------------------------------|
| WinMTR statistics |
| Host - % | Sent | Recv | Best | Avrg | Wrst | Last |
|------------------------------------------------|------|------|------|------|------|------|
| 192.168.1.1 - 10 | 183 | 166 | 0 | 0 | 5 | 0 |
|239.red-81-46-38.customer.static.ccgg.telefonica.net - 0 | 322 | 322 | 1 | 8 | 110 | 7 |
|169.red-81-46-45.customer.static.ccgg.telefonica.net - 0 | 322 | 322 | 2 | 6 | 97 | 5 |
|245.red-81-46-45.customer.static.ccgg.telefonica.net - 0 | 322 | 322 | 3 | 7 | 88 | 4 |
| 1.red-80-58-78.staticip.rima-tde.net - 0 | 322 | 322 | 2 | 7 | 79 | 2 |
|xe-7-1-2-65-graarctw1.net.telefonicaglobalsolutions.com - 0 | 322 | 322 | 11 | 14 | 119 | 11 |
|valve-be40-grtmadix2.net.telefonicaglobalsolutions.com - 0 | 322 | 322 | 10 | 14 | 98 | 11 |
| 155-133-246-212.valve.net - 0 | 322 | 322 | 10 | 14 | 95 | 10 |
| 155-133-246-50.valve.net - 0 | 322 | 322 | 9 | 13 | 105 | 9 |
|________________________________________________|______|______|______|______|______|______|
WinMTR v0.92 GPL V2 by Appnor MSP - Fully Managed Hosting & Cloud Provider
Y a 0.1s
|------------------------------------------------------------------------------------------|
| WinMTR statistics |
| Host - % | Sent | Recv | Best | Avrg | Wrst | Last |
|------------------------------------------------|------|------|------|------|------|------|
| 192.168.1.1 - 17 | 55 | 46 | 0 | 0 | 1 | 0 |
|239.red-81-46-38.customer.static.ccgg.telefonica.net - 0 | 460 | 460 | 2 | 10 | 145 | 19 |
|169.red-81-46-45.customer.static.ccgg.telefonica.net - 0 | 460 | 460 | 3 | 8 | 142 | 6 |
|245.red-81-46-45.customer.static.ccgg.telefonica.net - 0 | 460 | 460 | 4 | 9 | 143 | 4 |
| 1.red-80-58-78.staticip.rima-tde.net - 0 | 460 | 460 | 3 | 8 | 143 | 7 |
|xe-7-1-2-65-graarctw1.net.telefonicaglobalsolutions.com - 0 | 460 | 460 | 12 | 16 | 151 | 12 |
|valve-be40-grtmadix2.net.telefonicaglobalsolutions.com - 0 | 460 | 460 | 11 | 15 | 150 | 12 |
| 155-133-246-212.valve.net - 0 | 460 | 460 | 11 | 15 | 150 | 12 |
| 155-133-246-50.valve.net - 0 | 460 | 460 | 10 | 15 | 149 | 11 |
|________________________________________________|______|______|______|______|______|______|
WinMTR v0.92 GPL V2 by Appnor MSP - Fully Managed Hosting & Cloud Provider
Se ve que el porcentaje de fallo empieza a subir. Teniendo en cuenta la cantidad de paquetes por segundo que requiere un juego como CS2 pueden andar por ahí los tiros del problema.