Why did my wax ring fail after 2 months?

Question

Background: Toilet in hall bathroom on 2nd floor; Toilet flange was cracked; Repaired by my contractor: Cut 3” PVC pipe to remove the broken flange. Used insert flange that fit inside the 3” PVC pipe, interior diameter 2.5"; there is a 90-degree elbow immediately beneath the toilet, After the flooring was laid, flange height about flooring = 3.16/16” = 0.1975”

Toilet installation: Done by my plumber,toilet did not rock.

Toilet starts to leak 2 months later: It leaks out the side of the toilet only when it is flushed. We have not had any toilet clogs where I needed to plunge the toilet.

Photos below: Wax ring after I pulled the toilet. Repaired toilet flange with insert, mounted on top of sub-floor.

Here is a picture of the toilet leaking out when flushed, and picture of toilet flange insert pulled and sub-floor is soaked.

Pulled up LVP flooring. Sub-floor soaked.

Opened up sub-floor. Very little water leaked down (luckily caught this leak quickly). There is a 90-degree elbow right beneath toilet.

Answer 1

It looks like the wax ring was placed on the flange and then the toilet was misaligned when it was placed on the ring and then straightened out. You can see in your photos that there's heavy wax on one side and little or no wax on the other. I have always positioned the wax ring on to the toilet and then lowered the toilet into place. The toilet needs to go straight down with no sideway motion. Marking the floor with masking tape where the toilet will go helps to do that.

Answer 2

This could be leaking for several reasons.

1. Looking at the compressed wax ring against the bottom of the toilet stool indicates that the wax was compressed very thin in some areas. This is likely due to the flange sitting at a level higher than the floor and when putting the stool in place initially it may have rocked some and left an area where the wax squeezed out too much and left an area that did not stay sealed.
2. The second issue may be due to the crappy type of flange repair kit that did not seal well just being shoved down in the standpipe in the floor. This type of flange repair device also seriously reduces the inside diameter of the drain through the adapter and can impeded the flow during a flush, especially a high volume flush type toilet stool. A far far better repair would be to cut back the piping in the floor beyond that right angle elbow and install new fittings (replacements are inexpensive) and flange that are all glued together.
3. There is an off chance that the contractor that did the original work had placed a rag in the standpipe to prevent debris from falling into the open sewer line and to block off rising sewer gas. I'm sure that it has happened many times that the toilet gets re-installed without removing the rag. The rag could still be in there partially down pipe and causing a partial blockage. When the toilet is flushed the rush of water is too much for the piping and it causes a backflow out through the flange area and crappy flange adapter. If this is the actual cause the delay of two months could be due to the back pressure of this overflow repeatedly working at the thin wax areas and eventually breaking through.