Could I have been getting hit by the 'Parameter Sniffing Problem'?

We have a procedure that has 5 select queries in it. What was interesting was that it appeared to hang on the fourth query after running fine after an hour. When I would drop the procedure and recreate it then we would have no issues until about another hour later and then again on the fourth query it would hang. I put the WITH RECOMPILE statement in the procedure and it is now working fine.
The procedure is submitted as usp_ProcedureName '1629975,1629981,1629985,1102195'. The parameter can have one number listed or there could be a list of 500.
At first I thought that we were getting hit by a bad index or statistic and I would rebuild the indexes and update the statistics. However, this didn't seem to resolve the issue.
Could I have been getting hit by the 'Parameter Sniffing Problem' or am I assuming too much here?

This is how the fourth query looks like:
---
Declare @tktList TABLE (tkt_num int)
insert into @tktList (tkt_num)
(SELECT value FROM fn_split(@al_tkt_num, ','))
---
SELECT
ops.ops_tkt_num,
poss.po_num,
poss.required_dt,
poss.qty_ord,
poss.qty_recvd,
drop_ship = prev_op.order_num,
poss.product_id,
ops.manuf_id,
ops.client_owned_ind,
ops.prod_type_cd
FROM @tktList AS tktList
INNER JOIN order_product op
ON op.ops_tkt_num = tktList.tkt_num -- only tkts from the given list
INNER JOIN order_prod_seg ops
ON ops.ops_tkt_num = op.ops_tkt_num -- all ops for this tkt
INNER JOIN po_seg_ship poss
ON poss.product_id = ops.product_id
AND poss.manuf_id = ops.manuf_id -- all shippings of prods from current ops ...
INNER JOIN purchase_order PO
ON PO.po_num = poss.po_num
AND PO.whse_id = op.whse_id -- ... in the same warehouse
LEFT OUTER JOIN order_product AS prev_op
ON prev_op.ops_tkt_num = Pps_tkt_num -- one row - previous (first?) tkt from PO if any (for drop_ship)
WHERE poss.reconciled_dt IS NULL
AND poss.status_cd = 'O'
AND PO.po_type = (case when ops.client_owned_ind='Y' then 'C' else 'V' End )
AND ( ops.client_owned_ind = 'N' OR
PO.client_id = ops.client_id AND PO.contract_cd = ops.contract_cd
)
AND (Pps_tkt_num IS NULL OR -- only PO w/o ops link or linked to to parent ops tkt (???)
dbo.f_get_all_prev_ops_tkts(op.ops_tkt_num) like (convert(varchar(10), Pps_tkt_num) + '%') )