The League One side said that completion would now be possible by the start of September.
The stands are of a bespoke construction and involve the manufacture of new roofs.
They will offer an improved spectator experience for supporters once completed.
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The club claimed that because their construction was more complex, its main contractor GL Events encountered unforeseen engineering issues in the supply chain.
Alternative arrangements have been made for all supporters affected, with seats being allocated elsewhere in the ground.
The new South West stand is due to be built on 16-18th August and will be in use for the match with Portsmouth on 21st August.
The new Bristol Energy family stand is due to be constructed on 3-5th September and used for the match with Plymouth on 8th September.